Re: [QE-users] Thermodynamics with DFT+U
Dear Eduardo, Yes, what you said is correct. Then all codes must be recompiled after this change. Greetings, Iurii From: users on behalf of EDUARDO ARIEL MENENDEZ PROUPIN Sent: Friday, January 19, 2024 17:15 To: users@lists.quantum-espresso.org Subject: Re: [QE-users] Thermodynamics with DFT+U Iurii , Thanks again. I am trying with determine_num_pert_only = .true. Running pw.x I got the error “Too many atoms. The dimensions of Hubbard_V must be increased” en el archivo. Browsing in the source files I see that I can solve it increasing the parameter natx in the file /home/software/qe-6.8/Modules/parameters.f90 INTEGER, PARAMETER :: natx = 50 Is that all I need? I have requested that to the cluster admin, as was unable to use the compilers, so I shall wait. >> The atom indexes are relative to the atoms in the unit cell and include the >> neighbor atoms in the eight surrounding unit cells. >Actually, the pw.x code generates a virtual 3x3x3 supercell with your real unit >cell inside of it. So in total there are 27 unit cells. I should have written 26 instead of eight. I was thinking in 2D, Kirk would have beaten me like he did with Khan. 🙂 Best regards Eduardo Dear Eduardo, > The atom indexes are relative to the atoms in the unit cell and include the > neighbor atoms in the eight surrounding unit cells. Actually, the pw.x code generates a virtual 3x3x3 supercell with your real unit cell inside of it. So in total there are 27 unit cells. > For defect calculations, I need to use a supercell with a different shape. > How can I transfer the parameters to the supercell? I think this just needs a > small code to generate the parameter file for the supercell. I can do it if this is not available. Is it? Yes, unfortunately the I and J couple indices will change if you change the shape of the original real cell. The algorithm can be found in PW/src/intersite_V.f90. You can run the HP code by setting determine_num_pert_only = .true. For DFT+U+V, it will only determine the indices of couples without running heavy linear-response calculations. So then you can use this new file with the new indices and add there the U and V values that you previously computed using a smaller cell. Eduardo A. Menéndez Proupin Departamento de Física Aplicada I Universidad de Sevilla Teléfono: +34 9554 20231 https://personal.us.es/emenendez/ https://personal.us.es/emenendez/docencia/ ___ The Quantum ESPRESSO community stands by the Ukrainian people and expresses its concerns about the devastating effects that the Russian military offensive has on their country and on the free and peaceful scientific, cultural, and economic cooperation amongst peoples ___ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list users@lists.quantum-espresso.org https://lists.quantum-espresso.org/mailman/listinfo/users
Re: [QE-users] Thermodynamics with DFT+U
Iurii , Thanks again. I am trying with determine_num_pert_only = .true. Running pw.x I got the error “Too many atoms. The dimensions of Hubbard_V must be increased” en el archivo. Browsing in the source files I see that I can solve it increasing the parameter natx in the file /home/software/qe-6.8/Modules/parameters.f90 INTEGER, PARAMETER :: natx = 50 Is that all I need? I have requested that to the cluster admin, as was unable to use the compilers, so I shall wait. >> The atom indexes are relative to the atoms in the unit cell and include the >> neighbor atoms in the eight surrounding unit cells. >Actually, the pw.x code generates a virtual 3x3x3 supercell with your real unit >cell inside of it. So in total there are 27 unit cells. I should have written 26 instead of eight. I was thinking in 2D, Kirk would have beaten me like he did with Khan. 🙂 Best regards Eduardo Dear Eduardo, > The atom indexes are relative to the atoms in the unit cell and include the > neighbor atoms in the eight surrounding unit cells. Actually, the pw.x code generates a virtual 3x3x3 supercell with your real unit cell inside of it. So in total there are 27 unit cells. > For defect calculations, I need to use a supercell with a different shape. > How can I transfer the parameters to the supercell? I think this just needs a > small code to generate the parameter file for the supercell. I can do it if this is not available. Is it? Yes, unfortunately the I and J couple indices will change if you change the shape of the original real cell. The algorithm can be found in PW/src/intersite_V.f90. You can run the HP code by setting determine_num_pert_only = .true. For DFT+U+V, it will only determine the indices of couples without running heavy linear-response calculations. So then you can use this new file with the new indices and add there the U and V values that you previously computed using a smaller cell. Eduardo A. Menéndez Proupin Departamento de Física Aplicada I Universidad de Sevilla Teléfono: +34 9554 20231 https://personal.us.es/emenendez/ https://personal.us.es/emenendez/docencia/ ___ The Quantum ESPRESSO community stands by the Ukrainian people and expresses its concerns about the devastating effects that the Russian military offensive has on their country and on the free and peaceful scientific, cultural, and economic cooperation amongst peoples ___ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list users@lists.quantum-espresso.org https://lists.quantum-espresso.org/mailman/listinfo/users
Re: [QE-users] Thermodynamics with DFT+U
Dear Eduardo, > The atom indexes are relative to the atoms in the unit cell and include the > neighbor atoms in the eight surrounding unit cells. Actually, the pw.x code generates a virtual 3x3x3 supercell with your real unit cell inside of it. So in total there are 27 unit cells. > For defect calculations, I need to use a supercell with a different shape. > How can I transfer the parameters to the supercell? I think this just needs a > small code to generate the parameter file for the supercell. I can do it if this is not available. Is it? Yes, unfortunately the I and J couple indices will change if you change the shape of the original real cell. The algorithm can be found in PW/src/intersite_V.f90. You can run the HP code by setting determine_num_pert_only = .true. For DFT+U+V, it will only determine the indices of couples without running heavy linear-response calculations. So then you can use this new file with the new indices and add there the U and V values that you previously computed using a smaller cell. * Another practical question. I could refine the calculations recomputing the parameters for the atoms and pairs close to the defects. How does the computation time scale? Considering that for a ten-atom unit cell, the HP calculation took 2 days with 12 cores, what can I expect for a supercell with 120 atoms? The scaling is cubic w.r.t. the number of atoms. But you can reduce the size of the k and q meshes. So overall it will be much more expensive than for the 10-atoms cell and you would need to use a HPC cluster. HTH Iurii -- Dr. Iurii TIMROV Tenure-track scientist Laboratory for Materials Simulations (LMS) Paul Scherrer Institut (PSI) CH-5232 Villigen, Switzerland +41 56 310 62 14 https://www.psi.ch/en/lms/people/iurii-timrov From: users on behalf of EDUARDO ARIEL MENENDEZ PROUPIN Sent: Friday, January 19, 2024 11:09 To: users@lists.quantum-espresso.org Subject: Re: [QE-users] Thermodynamics with DFT+U Dear Iurii, Your explanations were quite useful and wide. I am still reading papers, but in fact I think I may have solved my problem for Fe2O3 with just U(Fe-d). I confirm that for Fe2O3, using the U(O-2p) computed with HP code cause a too large band gap (~4 ev). Using U(Fe-d) and V(Fe-O) gives a slightly large bangap (2.74 eV vs experimental range 2-2.6 eV). Using just U(Fe-d) I got a gap of 2.43 eV, which is inside the experimental range. Anyway, I still wish to have DFT+U+V as an option. The experimental gap may be corrected by future measurements, or it may be affected by zero-point motion, or maybe other property may need the V, e.g., magnetic moments. Then I have a practical problem. The parameter file, that contains the indexes of every pair of Fe and O atoms, was computed with a unit cell. The atom indexes are relative to the atoms in the unit cell and include the neighbor atoms in the eight surrounding unit cells. For defect calculations, I need to use a supercell with a different shape. How can I transfer the parameters to the supercell? I think this just needs a small code to generate the parameter file for the supercell. I can do it if this is not available. Is it? Another practical question. I could refine the calculations recomputing the parameters for the atoms and pairs close to the defects. How does the computation time scale? Considering that for a ten-atom unit cell, the HP calculation took 2 days with 12 cores, what can I expect for a supercell with 120 atoms? Eduardo A. Menéndez Proupin Departamento de Física Aplicada I Universidad de Sevilla Teléfono: +34 9554 20231 https://personal.us.es/emenendez/ https://personal.us.es/emenendez/docencia/ De: Timrov Iurii Enviado: lunes, 11 de diciembre de 2023 12:03 Para: users@lists.quantum-espresso.org Asunto: Re: [QE-users] Thermodynamics with DFT+U Dear Eduardo, Your questions are tricky. There is a lot one can say. Please see my comments below. Maybe someone else can have a different viewpoint and comment as well. * Should we choose one average value, or use the computed value for each system? Both options are used in the literature. From my experience, it is better to use the second one. * In DFT+U with empirical U people often use one value and compare the total energies. Why? One reason is because how would you choose different U values for different systems (e.g. FM vs AFM)? Maybe this can be done, but it is easier to use one empirical value. And it is claimed that the total energies must be compared with the same U value. But why? Is there a theorem or a proof? See below for the discussion why I would not use the same U value. * In the second case, one uses different U values for different structures, provided that these U value are computed ab initio. Does this make sense? At least to me, ye
Re: [QE-users] Thermodynamics with DFT+U
Dear Iurii, Your explanations were quite useful and wide. I am still reading papers, but in fact I think I may have solved my problem for Fe2O3 with just U(Fe-d). I confirm that for Fe2O3, using the U(O-2p) computed with HP code cause a too large band gap (~4 ev). Using U(Fe-d) and V(Fe-O) gives a slightly large bangap (2.74 eV vs experimental range 2-2.6 eV). Using just U(Fe-d) I got a gap of 2.43 eV, which is inside the experimental range. Anyway, I still wish to have DFT+U+V as an option. The experimental gap may be corrected by future measurements, or it may be affected by zero-point motion, or maybe other property may need the V, e.g., magnetic moments. Then I have a practical problem. The parameter file, that contains the indexes of every pair of Fe and O atoms, was computed with a unit cell. The atom indexes are relative to the atoms in the unit cell and include the neighbor atoms in the eight surrounding unit cells. For defect calculations, I need to use a supercell with a different shape. How can I transfer the parameters to the supercell? I think this just needs a small code to generate the parameter file for the supercell. I can do it if this is not available. Is it? Another practical question. I could refine the calculations recomputing the parameters for the atoms and pairs close to the defects. How does the computation time scale? Considering that for a ten-atom unit cell, the HP calculation took 2 days with 12 cores, what can I expect for a supercell with 120 atoms? Eduardo A. Menéndez Proupin Departamento de Física Aplicada I Universidad de Sevilla Teléfono: +34 9554 20231 https://personal.us.es/emenendez/ https://personal.us.es/emenendez/docencia/ De: Timrov Iurii Enviado: lunes, 11 de diciembre de 2023 12:03 Para: users@lists.quantum-espresso.org Asunto: Re: [QE-users] Thermodynamics with DFT+U Dear Eduardo, Your questions are tricky. There is a lot one can say. Please see my comments below. Maybe someone else can have a different viewpoint and comment as well. * Should we choose one average value, or use the computed value for each system? Both options are used in the literature. From my experience, it is better to use the second one. * In DFT+U with empirical U people often use one value and compare the total energies. Why? One reason is because how would you choose different U values for different systems (e.g. FM vs AFM)? Maybe this can be done, but it is easier to use one empirical value. And it is claimed that the total energies must be compared with the same U value. But why? Is there a theorem or a proof? See below for the discussion why I would not use the same U value. * In the second case, one uses different U values for different structures, provided that these U value are computed ab initio. Does this make sense? At least to me, yes. Why? Because different structures require different corrections. And, indeed, if one computes U e.g. for the Co-3d states in LiCoO2 and CoO2, the U values appear to be different. Why? Because the electronic screening is different, and the magnitude of self-interaction errors is different in LiCoO2 and CoO2. One can make an approximation and use an average U value for these two systems, but why doing so? From our experience using different ab initio U values and comparing total energies gives results in good agreement with experiments (e.g. voltages for batteries). But we do not have a (mathematical) justification for doing so, as well as we do not have a proof why one should not do it. Hence, at present there is no consensus in the literature on this topic. More investigations for various systems is needed to see trends. But for me, comparing total energies with different U values obtained from linear-response theory makes sense and it provides reasonable results. * Concerning the advantage of self consistency, let me rise the example LiCoO2 that comes with the HP code. The example produces U for Co and also for O, as well as V(Co-O). U(O-2p)=8.0439 eV. Is this parameter useful? As the example is not converged w.r.t. to k-points and cutoffs the number may change, but U(O-2p) is still there. I read PRB101, 064305 (2020) by Floris et al, and it seems that U(O-2p) is discarded. I am curious why, but I couldn't find a discussion. Maybe there is another article. My point here is that using self consistent parameters for some elements and shells, and discarding others is just a partial self-consistency. We did not apply the U correction to O-2p states. The question of whether to apply or not the U correction to O-2p is another big question. Many things can be said here, and you will possibly receive different answers from different people. A few comments from my side: * We generally do not apply U to O-2p, when U is computed from linear-response theory, because it is large (8-9 eV) and from our experience the accuracy of
Re: [QE-users] Thermodynamics with DFT+U
Dear Cyrille, All, Thanks for your comment! Indeed, LS vs HS for molecules containing transition-metal elements is a challenging problem for DFT+U. I would like to draw your attention to our paper describing the orbital-resolved DFT+U approach that is now available on arXiv and that address this problem: https://arxiv.org/abs/2312.13580 Greetings, Iurii -- Dr. Iurii TIMROV Tenure-track scientist Laboratory for Materials Simulations (LMS) Paul Scherrer Institut (PSI) CH-5232 Villigen, Switzerland +41 56 310 62 14 https://www.psi.ch/en/lms/people/iurii-timrov From: users on behalf of BARRETEAU Cyrille Sent: Tuesday, December 12, 2023 11:46 To: users@lists.quantum-espresso.org Subject: Re: [QE-users] Thermodynamics with DFT+U Hi In fact I faced the same type of problem when modelling spin-crossover molecules. In such molecular systems the standard DFT fails to describe the energy balance between Low Spin (LS) and High Spin (HS) state. The LS being strongly favoured. Adding U is a way to circumvent this issue. But trying to determine U self-consistently does not work (at least for our system). Indeed we face the same nasty question that you raised: we have a drastically different U for LS and HS and the energy balance obtained is clearly incorrect. In addition in such system the atomic relaxation is very crucial, hence one also has to take into account a combined scf+relax determination of U that rapidly drives you crazy:-) We have finally abandoned this procedure to keep a constant a U, that we determine from experimental estimation of E_LS-E_HS. Another approach consists in using hybrid functional. But we also have a similar problem due to the ratio of exact exchange.. Indeed the "traditional" 1/4 ratio is too large to describe the energy balance, strongly favouring HS this time! Hence one has to decrease the ratio down to something like 0.15... Cyrille Cyrille Barreteau CEA Saclay, IRAMIS, SPEC Bat. 771 91191 Gif sur Yvette Cedex, FRANCE +33 1 69 08 38 56 /+33 6 47 53 66 52 (mobile) email: cyrille.barret...@cea.fr Website: http://iramis.cea.fr/Pisp/cyrille.barreteau/ COSMICS: http://cosmics-h2020.eu/ De : users de la part de Timrov Iurii Envoyé : lundi 11 décembre 2023 12:03:32 À : users@lists.quantum-espresso.org Objet : Re: [QE-users] Thermodynamics with DFT+U Dear Eduardo, Your questions are tricky. There is a lot one can say. Please see my comments below. Maybe someone else can have a different viewpoint and comment as well. * Should we choose one average value, or use the computed value for each system? Both options are used in the literature. From my experience, it is better to use the second one. * In DFT+U with empirical U people often use one value and compare the total energies. Why? One reason is because how would you choose different U values for different systems (e.g. FM vs AFM)? Maybe this can be done, but it is easier to use one empirical value. And it is claimed that the total energies must be compared with the same U value. But why? Is there a theorem or a proof? See below for the discussion why I would not use the same U value. * In the second case, one uses different U values for different structures, provided that these U value are computed ab initio. Does this make sense? At least to me, yes. Why? Because different structures require different corrections. And, indeed, if one computes U e.g. for the Co-3d states in LiCoO2 and CoO2, the U values appear to be different. Why? Because the electronic screening is different, and the magnitude of self-interaction errors is different in LiCoO2 and CoO2. One can make an approximation and use an average U value for these two systems, but why doing so? From our experience using different ab initio U values and comparing total energies gives results in good agreement with experiments (e.g. voltages for batteries). But we do not have a (mathematical) justification for doing so, as well as we do not have a proof why one should not do it. Hence, at present there is no consensus in the literature on this topic. More investigations for various systems is needed to see trends. But for me, comparing total energies with different U values obtained from linear-response theory makes sense and it provides reasonable results. * Concerning the advantage of self consistency, let me rise the example LiCoO2 that comes with the HP code. The example produces U for Co and also for O, as well as V(Co-O). U(O-2p)=8.0439 eV. Is this parameter useful? As the example is not converged w.r.t. to k-points and cutoffs the number may change, but U(O-2p) is still there. I read PRB101, 064305 (2020) by Floris et al, and it seems that U(O-2p) is di
Re: [QE-users] Thermodynamics with DFT+U
Hi In fact I faced the same type of problem when modelling spin-crossover molecules. In such molecular systems the standard DFT fails to describe the energy balance between Low Spin (LS) and High Spin (HS) state. The LS being strongly favoured. Adding U is a way to circumvent this issue. But trying to determine U self-consistently does not work (at least for our system). Indeed we face the same nasty question that you raised: we have a drastically different U for LS and HS and the energy balance obtained is clearly incorrect. In addition in such system the atomic relaxation is very crucial, hence one also has to take into account a combined scf+relax determination of U that rapidly drives you crazy:-) We have finally abandoned this procedure to keep a constant a U, that we determine from experimental estimation of E_LS-E_HS. Another approach consists in using hybrid functional. But we also have a similar problem due to the ratio of exact exchange.. Indeed the "traditional" 1/4 ratio is too large to describe the energy balance, strongly favouring HS this time! Hence one has to decrease the ratio down to something like 0.15... Cyrille Cyrille Barreteau CEA Saclay, IRAMIS, SPEC Bat. 771 91191 Gif sur Yvette Cedex, FRANCE +33 1 69 08 38 56 /+33 6 47 53 66 52 (mobile) email: cyrille.barret...@cea.fr Website: http://iramis.cea.fr/Pisp/cyrille.barreteau/ COSMICS: http://cosmics-h2020.eu/ De : users de la part de Timrov Iurii Envoyé : lundi 11 décembre 2023 12:03:32 À : users@lists.quantum-espresso.org Objet : Re: [QE-users] Thermodynamics with DFT+U Dear Eduardo, Your questions are tricky. There is a lot one can say. Please see my comments below. Maybe someone else can have a different viewpoint and comment as well. * Should we choose one average value, or use the computed value for each system? Both options are used in the literature. From my experience, it is better to use the second one. * In DFT+U with empirical U people often use one value and compare the total energies. Why? One reason is because how would you choose different U values for different systems (e.g. FM vs AFM)? Maybe this can be done, but it is easier to use one empirical value. And it is claimed that the total energies must be compared with the same U value. But why? Is there a theorem or a proof? See below for the discussion why I would not use the same U value. * In the second case, one uses different U values for different structures, provided that these U value are computed ab initio. Does this make sense? At least to me, yes. Why? Because different structures require different corrections. And, indeed, if one computes U e.g. for the Co-3d states in LiCoO2 and CoO2, the U values appear to be different. Why? Because the electronic screening is different, and the magnitude of self-interaction errors is different in LiCoO2 and CoO2. One can make an approximation and use an average U value for these two systems, but why doing so? From our experience using different ab initio U values and comparing total energies gives results in good agreement with experiments (e.g. voltages for batteries). But we do not have a (mathematical) justification for doing so, as well as we do not have a proof why one should not do it. Hence, at present there is no consensus in the literature on this topic. More investigations for various systems is needed to see trends. But for me, comparing total energies with different U values obtained from linear-response theory makes sense and it provides reasonable results. * Concerning the advantage of self consistency, let me rise the example LiCoO2 that comes with the HP code. The example produces U for Co and also for O, as well as V(Co-O). U(O-2p)=8.0439 eV. Is this parameter useful? As the example is not converged w.r.t. to k-points and cutoffs the number may change, but U(O-2p) is still there. I read PRB101, 064305 (2020) by Floris et al, and it seems that U(O-2p) is discarded. I am curious why, but I couldn't find a discussion. Maybe there is another article. My point here is that using self consistent parameters for some elements and shells, and discarding others is just a partial self-consistency. We did not apply the U correction to O-2p states. The question of whether to apply or not the U correction to O-2p is another big question. Many things can be said here, and you will possibly receive different answers from different people. A few comments from my side: * We generally do not apply U to O-2p, when U is computed from linear-response theory, because it is large (8-9 eV) and from our experience the accuracy of some properties (e.g. voltages) are worsened. * If you use ACBN0 to compute U, you might get 2-3 eV, and applying this correction to O-2p might impr
Re: [QE-users] Thermodynamics with DFT+U
stent parameters is correct. Another excellent question. In Quantum ESPRESSO, U is constant and its derivative dU/dR is set to zero when computing Hubbard forces (and same for Hubbard stresses): https://journals.aps.org/prb/abstract/10.1103/PhysRevB.102.235159 In order to circumvent this problem, we perform the calculation of U in a self-consistent fashion, by performing cyclic calculations (recalculation of U and structural optimization with DFT+U), thus pushing the system to the energy extremum: https://journals.aps.org/prb/abstract/10.1103/PhysRevB.103.045141 HTH Greetings, Iurii -- Dr. Iurii TIMROV Tenure-track scientist Laboratory for Materials Simulations (LMS) Paul Scherrer Institut (PSI) CH-5232 Villigen, Switzerland +41 56 310 62 14 https://www.psi.ch/en/lms/people/iurii-timrov From: users on behalf of EDUARDO ARIEL MENENDEZ PROUPIN Sent: Wednesday, December 6, 2023 10:24 To: users@lists.quantum-espresso.org Subject: Re: [QE-users] Thermodynamics with DFT+U Hello! I have read this thread, which is from three years ago, and I would like to know if there is any update, consensus, or a study about this issue. The topic of the thread was how to compare the energies of two systems when there is at least one element subject to Hubbard correction, in the case that the Hubbard parameters are computed self-consistently via the HP code, and have different values in the two systems compared. Should we choose one average value, or use the computed value for each system? The two systems may be either: 1. Two phases of a material 2. Two antiferromagnetic configurations 3. Crystal with a transition metal impurity vs clean crystal and impurity in bulk metal. I may have a case of type (b), with certain energy order when using the self-consistent U values for each AFM configuration, and the opposite order when the same U is used for both configurations. The same U was computed for one configuration, I am waiting for the queue to finish calculations with the other U, but this is published (Naveas et al, https://doi.org/10.1016/j.isci.2023.106033). Concerning the advantage of self consistency, let me rise the example LiCoO2 that comes with the HP code. The example produces U for Co and also for O, as well as V(Co-O). U(O-2p)=8.0439 eV. Is this parameter useful? As the example is not converged w.r.t. to k-points and cutoffs the number may change, but U(O-2p) is still there. I read PRB101, 064305 (2020) by Floris et al, and it seems that U(O-2p) is discarded. I am curious why, but I couldn't find a discussion. Maybe there is another article. My point here is that using self consistent parameters for some elements and shells, and discarding others is just a partial self-consistency. A related question is whether the forces and energies are consistent with variable U and V. That is, Let us move the Fe impurity atom inside a crystal, and recompute the U and V for each position. Force is the gradient of energy obtained in the Hellman-Feynman way, I guess with constant U,V. Pressure is the negative of the derivative of the energy with respect to volume, which implies a variation of U and V. I guess the stress is computed with constant U, V. I think that self-consistency could be implemented, but first we must be sure that comparing energies with variable, self-consistent parameters is correct. Best regards, Eduardo A. Menéndez Proupin Departamento de Física Aplicada I Universidad de Sevilla Teléfono: +34 9554 20231 https://personal.us.es/emenendez/ https://personal.us.es/emenendez/docencia/ ___ The Quantum ESPRESSO community stands by the Ukrainian people and expresses its concerns about the devastating effects that the Russian military offensive has on their country and on the free and peaceful scientific, cultural, and economic cooperation amongst peoples ___ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list users@lists.quantum-espresso.org https://lists.quantum-espresso.org/mailman/listinfo/users
Re: [QE-users] Thermodynamics with DFT+U
Hello! I have read this thread, which is from three years ago, and I would like to know if there is any update, consensus, or a study about this issue. The topic of the thread was how to compare the energies of two systems when there is at least one element subject to Hubbard correction, in the case that the Hubbard parameters are computed self-consistently via the HP code, and have different values in the two systems compared. Should we choose one average value, or use the computed value for each system? The two systems may be either: 1. Two phases of a material 2. Two antiferromagnetic configurations 3. Crystal with a transition metal impurity vs clean crystal and impurity in bulk metal. I may have a case of type (b), with certain energy order when using the self-consistent U values for each AFM configuration, and the opposite order when the same U is used for both configurations. The same U was computed for one configuration, I am waiting for the queue to finish calculations with the other U, but this is published (Naveas et al, https://doi.org/10.1016/j.isci.2023.106033). Concerning the advantage of self consistency, let me rise the example LiCoO2 that comes with the HP code. The example produces U for Co and also for O, as well as V(Co-O). U(O-2p)=8.0439 eV. Is this parameter useful? As the example is not converged w.r.t. to k-points and cutoffs the number may change, but U(O-2p) is still there. I read PRB101, 064305 (2020) by Floris et al, and it seems that U(O-2p) is discarded. I am curious why, but I couldn't find a discussion. Maybe there is another article. My point here is that using self consistent parameters for some elements and shells, and discarding others is just a partial self-consistency. A related question is whether the forces and energies are consistent with variable U and V. That is, Let us move the Fe impurity atom inside a crystal, and recompute the U and V for each position. Force is the gradient of energy obtained in the Hellman-Feynman way, I guess with constant U,V. Pressure is the negative of the derivative of the energy with respect to volume, which implies a variation of U and V. I guess the stress is computed with constant U, V. I think that self-consistency could be implemented, but first we must be sure that comparing energies with variable, self-consistent parameters is correct. Best regards, Eduardo A. Menéndez Proupin Departamento de Física Aplicada I Universidad de Sevilla Teléfono: +34 9554 20231 https://personal.us.es/emenendez/ https://personal.us.es/emenendez/docencia/ ___ The Quantum ESPRESSO community stands by the Ukrainian people and expresses its concerns about the devastating effects that the Russian military offensive has on their country and on the free and peaceful scientific, cultural, and economic cooperation amongst peoples ___ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list users@lists.quantum-espresso.org https://lists.quantum-espresso.org/mailman/listinfo/users
Re: [QE-users] Thermodynamics with DFT+U
Dear Ilya, Thanks for your comment! > But in general, the study of this interesting question seems to be a real > scientific challenge. Yes, indeed Greetings, Iurii -- Dr. Iurii TIMROV Postdoctoral Researcher STI - IMX - THEOS and NCCR - MARVEL Swiss Federal Institute of Technology Lausanne (EPFL) CH-1015 Lausanne, Switzerland +41 21 69 34 881 http://people.epfl.ch/265334 From: users on behalf of Ilya Ryabinkin Sent: Friday, October 30, 2020 12:34:04 PM To: Quantum ESPRESSO users Forum Subject: Re: [QE-users] Thermodynamics with DFT+U Dear Yuriii: Treating U as a response property may not be sufficient. Response properties are not bound neither from above nor from below, and a particular (valid!) value of U may still correspond to unphysical values of energy due to the approximate nature of DFT+U. The situation is somewhat similar to using self-consistent vs HF densities in DFT to get the total energies (see K.Burke works on that). But in general, the study of this interesting question seems to be a real scientific challenge. -- Ilya Ryabinkin, Senior Research Fellow, OTI Lumionics Inc Toronto, Canada. On Thu, Oct 29, 2020 at 1:37 PM Timrov Iurii mailto:iurii.tim...@epfl.ch>> wrote: Dear Giuseppe, Thank you for your comment! > In principle you are right, but if you try to compute, e.g., formation > heats or formation energy of defects by using different U values (I > did it long time ago in the case of TiO2 related studies for metallic > Ti, for TiO2, for Ti2O3) you fall sometimes very far from experimental > references, farther then using non corrected GGA. Ok, I see. So you used semiempirical U and things got worse, right? It would be interesting to see what happens if ab initio U is used for each structure. > I've used semiempirically averaged values in a lot of studies (including the > correction of O- and N-related bands in oxides and nitrides) and > things are a bit semiempirical, obviously, but still quite improved > with respect to GGA. As long as you motivate what you are doing, I do > not see particular harm in semiempirical U corrections! Ok. Of course, one is free to choose whether to use a semiempirical or ab initio U. But I see the following issues when using semiempirical U: - choice of the Hubbard manifold. U depends a lot on the Hubbard manifold (atomic, ortho-atomic, Wannier functions, etc.). Different codes use different Hubbard manifolds. So if one takes U from some paper where it was determined semiempirically (e.g. using VASP) and use it in QE (with a different manifold) the results can be totally different - choice of the pseudopotential (see Appendix in J. Chem. Phys. 129, 134314 (2008)). From this reference you can see that the pseudopotentials generated in different oxidation states require different U. It is easy to compute U for a given pseudo, but how to determine it semiempirically (try to reproduce some experimental quantity? and what to do if there is no experimental data for the material under investigation?) - choice the exchange-correlation functional: PW91, PBE, PBEsol, ... - each time the U correction is not exactly the same. For each functional U must be tuned by hand if done semiempirically. So for a given computational setup (Hubbard manifold, pseudos, functional, etc.) I would simply compute U from first principles (luckily we have now theories and codes to do that, which was not the case in the past). And when one wants to do a high-throughput study for thousands of materials, fitting U for each system to the experimental data would kill the whole idea of high-throughput. Just my thoughts. Thanks! Greetings, Iurii -- Dr. Iurii TIMROV Postdoctoral Researcher STI - IMX - THEOS and NCCR - MARVEL Swiss Federal Institute of Technology Lausanne (EPFL) CH-1015 Lausanne, Switzerland +41 21 69 34 881 http://people.epfl.ch/265334 From: users mailto:users-boun...@lists.quantum-espresso.org>> on behalf of Giuseppe Mattioli mailto:giuseppe.matti...@ism.cnr.it>> Sent: Thursday, October 29, 2020 5:58:39 PM To: Quantum ESPRESSO users Forum Subject: Re: [QE-users] Thermodynamics with DFT+U Dear Iurii In principle you are right, but if you try to compute, e.g., formation heats or formation energy of defects by using different U values (I did it long time ago in the case of TiO2 related studies for metallic Ti, for TiO2, for Ti2O3) you fall sometimes very far from experimental references, farther then using non corrected GGA. I've used semiempirically averaged values in a lot of studies (including the correction of O- and N-related bands in oxides and nitrides) and things are a bit semiempirical, obviously, but still quite improved with respect to GGA. As long as you motivate what you are doing, I do not see particular harm in semiempirical U corrections! Best Giuseppe Quoting Timro
Re: [QE-users] Thermodynamics with DFT+U
Dear Yuriii: Treating U as a response property may not be sufficient. Response properties are not bound neither from above nor from below, and a particular (valid!) value of U may still correspond to unphysical values of energy due to the approximate nature of DFT+U. The situation is somewhat similar to using self-consistent vs HF densities in DFT to get the total energies (see K.Burke works on that). But in general, the study of this interesting question seems to be a real scientific challenge. -- Ilya Ryabinkin, Senior Research Fellow, OTI Lumionics Inc Toronto, Canada. On Thu, Oct 29, 2020 at 1:37 PM Timrov Iurii wrote: > Dear Giuseppe, > > > Thank you for your comment! > > > > In principle you are right, but if you try to compute, e.g., formation > > heats or formation energy of defects by using different U values (I > > did it long time ago in the case of TiO2 related studies for metallic > > Ti, for TiO2, for Ti2O3) you fall sometimes very far from experimental > > references, farther then using non corrected GGA. > > > Ok, I see. So you used semiempirical U and things got worse, right? It > would be interesting to see what happens if ab initio U is used for each > structure. > > > > I've used semiempirically averaged values in a lot of studies > (including the > > correction of O- and N-related bands in oxides and nitrides) and > > things are a bit semiempirical, obviously, but still quite improved > > with respect to GGA. As long as you motivate what you are doing, I do > > not see particular harm in semiempirical U corrections! > > > Ok. Of course, one is free to choose whether to use a semiempirical or ab > initio U. But I see the following issues when using semiempirical U: > > - choice of the Hubbard manifold. U depends a lot on the Hubbard manifold > (atomic, ortho-atomic, Wannier functions, etc.). Different codes use > different Hubbard manifolds. So if one takes U from some paper where it was > determined semiempirically (e.g. using VASP) and use it in QE (with a > different manifold) the results can be totally different > > - choice of the pseudopotential (see Appendix in J. Chem. Phys. 129, > 134314 (2008)). From this reference you can see that the pseudopotentials > generated in different oxidation states require different U. It is easy to > compute U for a given pseudo, but how to determine it semiempirically (try > to reproduce some experimental quantity? and what to do if there is no > experimental data for the material under investigation?) > > - choice the exchange-correlation functional: PW91, PBE, PBEsol, ... - > each time the U correction is not exactly the same. For each functional U > must be tuned by hand if done semiempirically. > > So for a given computational setup (Hubbard manifold, pseudos, functional, > etc.) I would simply compute U from first principles (luckily we have now > theories and codes to do that, which was not the case in the past). And > when one wants to do a high-throughput study for thousands of materials, > fitting U for each system to the experimental data would kill the whole > idea of high-throughput. Just my thoughts. > > > Thanks! > > > Greetings, > > Iurii > > > -- > Dr. Iurii TIMROV > Postdoctoral Researcher > STI - IMX - THEOS and NCCR - MARVEL > Swiss Federal Institute of Technology Lausanne (EPFL) > CH-1015 Lausanne, Switzerland > +41 21 69 34 881 > http://people.epfl.ch/265334 > -- > *From:* users on behalf of > Giuseppe Mattioli > *Sent:* Thursday, October 29, 2020 5:58:39 PM > *To:* Quantum ESPRESSO users Forum > *Subject:* Re: [QE-users] Thermodynamics with DFT+U > > > Dear Iurii > In principle you are right, but if you try to compute, e.g., formation > heats or formation energy of defects by using different U values (I > did it long time ago in the case of TiO2 related studies for metallic > Ti, for TiO2, for Ti2O3) you fall sometimes very far from experimental > references, farther then using non corrected GGA. I've used > semiempirically averaged values in a lot of studies (including the > correction of O- and N-related bands in oxides and nitrides) and > things are a bit semiempirical, obviously, but still quite improved > with respect to GGA. As long as you motivate what you are doing, I do > not see particular harm in semiempirical U corrections! > Best > Giuseppe > > Quoting Timrov Iurii : > > > Dear Malte, > > > > > > This is not an easy question. Let me express my opinion. > > > > > >> I read many times in papers that I should not compare total energies of > >> DFT+U calculations with different U values. > > > >
Re: [QE-users] Thermodynamics with DFT+U
Dear Iurii, dear Giuseppe, thank you for the interesting discussion. My "knowledge" comes from papers using empirical U values. I see that my question is still related to an ongoing debate. However, your arguments and references helped my for my discussion. Thanks a lot, best regards, Malte Am 29.10.20 um 18:36 schrieb Timrov Iurii: Dear Giuseppe, Thank you for your comment! > In principle you are right, but if you try to compute, e.g., formation > heats or formation energy of defects by using different U values (I > did it long time ago in the case of TiO2 related studies for metallic > Ti, for TiO2, for Ti2O3) you fall sometimes very far from experimental > references, farther then using non corrected GGA. Ok, I see. Soyou used semiempirical U and things got worse, right? It would be interesting to see what happens if ab initio U is used for each structure. > I've used semiempirically averaged values in a lot of studies (including the > correction of O- and N-related bands in oxides and nitrides) and > things are a bit semiempirical, obviously, but still quite improved > with respect to GGA. As long as you motivate what you are doing, I do > not see particular harm in semiempirical U corrections! Ok. Of course, one is free to choose whether to use a semiempirical or ab initio U. But I see the following issues when using semiempirical U: - choice of the Hubbard manifold. U depends a lot on the Hubbard manifold (atomic, ortho-atomic, Wannier functions, etc.). Different codes use different Hubbard manifolds. So if one takes U from some paper where it was determined semiempirically (e.g. using VASP) and use it in QE (with a different manifold) the results can be totally different - choice of the pseudopotential (see Appendix in J. Chem. Phys. 129, 134314 (2008)). From this reference you can see that the pseudopotentials generated in different oxidation states require different U. It is easy to compute U for a given pseudo, but how to determine it semiempirically (try to reproduce some experimental quantity? and what to do if there is no experimental data for the material under investigation?) - choice the exchange-correlation functional: PW91, PBE, PBEsol, ... - each time the U correction is not exactly the same. For each functional U must be tuned by hand if done semiempirically. So for a given computational setup (Hubbard manifold, pseudos, functional, etc.) I would simply compute U from first principles (luckily we have now theories and codes to do that, which was not the case in the past). And when one wants to do a high-throughput study for thousands of materials, fitting U for each system to the experimental data would kill the whole idea of high-throughput. Just my thoughts. Thanks! Greetings, Iurii -- Dr. Iurii TIMROV Postdoctoral Researcher STI - IMX - THEOSand NCCR - MARVEL Swiss Federal Institute of Technology Lausanne (EPFL) CH-1015 Lausanne, Switzerland +41 21 69 34 881 http://people.epfl.ch/265334 *From:* users on behalf of Giuseppe Mattioli *Sent:* Thursday, October 29, 2020 5:58:39 PM *To:* Quantum ESPRESSO users Forum *Subject:* Re: [QE-users] Thermodynamics with DFT+U Dear Iurii In principle you are right, but if you try to compute, e.g., formation heats or formation energy of defects by using different U values (I did it long time ago in the case of TiO2 related studies for metallic Ti, for TiO2, for Ti2O3) you fall sometimes very far from experimental references, farther then using non corrected GGA. I've used semiempirically averaged values in a lot of studies (including the correction of O- and N-related bands in oxides and nitrides) and things are a bit semiempirical, obviously, but still quite improved with respect to GGA. As long as you motivate what you are doing, I do not see particular harm in semiempirical U corrections! Best Giuseppe Quoting Timrov Iurii : > Dear Malte, > > > This is not an easy question. Let me express my opinion. > > >> I read many times in papers that I should not compare total energies of >> DFT+U calculations with different U values. > > > Can you give some references please? > > > Well the problem is that in literature often people still use > empirical values of U. In this case, I agree that the comparison of > energies will depend strongly on U which one chooses based on some > arguments. But if one computes U from first principles, then U is a > response property of each system (and the response is different in > each system, hence different U) then it makes sense to me to compare > energies (but I am not aware of any theoretical proof that it is > allowed to do so). > > > For example, in LiCoO2 the computed value of U for Co-3d is 6.91 eV, > while U for Co-3d in CoO is 4.55 eV (b
Re: [QE-users] Thermodynamics with DFT+U
Dear Giuseppe, Thank you for your comment! > In principle you are right, but if you try to compute, e.g., formation > heats or formation energy of defects by using different U values (I > did it long time ago in the case of TiO2 related studies for metallic > Ti, for TiO2, for Ti2O3) you fall sometimes very far from experimental > references, farther then using non corrected GGA. Ok, I see. So you used semiempirical U and things got worse, right? It would be interesting to see what happens if ab initio U is used for each structure. > I've used semiempirically averaged values in a lot of studies (including the > correction of O- and N-related bands in oxides and nitrides) and > things are a bit semiempirical, obviously, but still quite improved > with respect to GGA. As long as you motivate what you are doing, I do > not see particular harm in semiempirical U corrections! Ok. Of course, one is free to choose whether to use a semiempirical or ab initio U. But I see the following issues when using semiempirical U: - choice of the Hubbard manifold. U depends a lot on the Hubbard manifold (atomic, ortho-atomic, Wannier functions, etc.). Different codes use different Hubbard manifolds. So if one takes U from some paper where it was determined semiempirically (e.g. using VASP) and use it in QE (with a different manifold) the results can be totally different - choice of the pseudopotential (see Appendix in J. Chem. Phys. 129, 134314 (2008)). From this reference you can see that the pseudopotentials generated in different oxidation states require different U. It is easy to compute U for a given pseudo, but how to determine it semiempirically (try to reproduce some experimental quantity? and what to do if there is no experimental data for the material under investigation?) - choice the exchange-correlation functional: PW91, PBE, PBEsol, ... - each time the U correction is not exactly the same. For each functional U must be tuned by hand if done semiempirically. So for a given computational setup (Hubbard manifold, pseudos, functional, etc.) I would simply compute U from first principles (luckily we have now theories and codes to do that, which was not the case in the past). And when one wants to do a high-throughput study for thousands of materials, fitting U for each system to the experimental data would kill the whole idea of high-throughput. Just my thoughts. Thanks! Greetings, Iurii -- Dr. Iurii TIMROV Postdoctoral Researcher STI - IMX - THEOS and NCCR - MARVEL Swiss Federal Institute of Technology Lausanne (EPFL) CH-1015 Lausanne, Switzerland +41 21 69 34 881 http://people.epfl.ch/265334 From: users on behalf of Giuseppe Mattioli Sent: Thursday, October 29, 2020 5:58:39 PM To: Quantum ESPRESSO users Forum Subject: Re: [QE-users] Thermodynamics with DFT+U Dear Iurii In principle you are right, but if you try to compute, e.g., formation heats or formation energy of defects by using different U values (I did it long time ago in the case of TiO2 related studies for metallic Ti, for TiO2, for Ti2O3) you fall sometimes very far from experimental references, farther then using non corrected GGA. I've used semiempirically averaged values in a lot of studies (including the correction of O- and N-related bands in oxides and nitrides) and things are a bit semiempirical, obviously, but still quite improved with respect to GGA. As long as you motivate what you are doing, I do not see particular harm in semiempirical U corrections! Best Giuseppe Quoting Timrov Iurii : > Dear Malte, > > > This is not an easy question. Let me express my opinion. > > >> I read many times in papers that I should not compare total energies of >> DFT+U calculations with different U values. > > > Can you give some references please? > > > Well the problem is that in literature often people still use > empirical values of U. In this case, I agree that the comparison of > energies will depend strongly on U which one chooses based on some > arguments. But if one computes U from first principles, then U is a > response property of each system (and the response is different in > each system, hence different U) then it makes sense to me to compare > energies (but I am not aware of any theoretical proof that it is > allowed to do so). > > > For example, in LiCoO2 the computed value of U for Co-3d is 6.91 eV, > while U for Co-3d in CoO is 4.55 eV (both using 'atomic' orbitals > and some pseudos on top of PBEsol - see PRB 101, 064305 (2020)). So > in both cases we consider Co-3d states, but the value of U is very > different. This is so because Co-3d states require different > corrections when they are in different chemical environments (these > Co-3d states hybridize differently with ligands in different > compounds). If you use a
Re: [QE-users] Thermodynamics with DFT+U
Dear Iurii In principle you are right, but if you try to compute, e.g., formation heats or formation energy of defects by using different U values (I did it long time ago in the case of TiO2 related studies for metallic Ti, for TiO2, for Ti2O3) you fall sometimes very far from experimental references, farther then using non corrected GGA. I've used semiempirically averaged values in a lot of studies (including the correction of O- and N-related bands in oxides and nitrides) and things are a bit semiempirical, obviously, but still quite improved with respect to GGA. As long as you motivate what you are doing, I do not see particular harm in semiempirical U corrections! Best Giuseppe Quoting Timrov Iurii : Dear Malte, This is not an easy question. Let me express my opinion. I read many times in papers that I should not compare total energies of DFT+U calculations with different U values. Can you give some references please? Well the problem is that in literature often people still use empirical values of U. In this case, I agree that the comparison of energies will depend strongly on U which one chooses based on some arguments. But if one computes U from first principles, then U is a response property of each system (and the response is different in each system, hence different U) then it makes sense to me to compare energies (but I am not aware of any theoretical proof that it is allowed to do so). For example, in LiCoO2 the computed value of U for Co-3d is 6.91 eV, while U for Co-3d in CoO is 4.55 eV (both using 'atomic' orbitals and some pseudos on top of PBEsol - see PRB 101, 064305 (2020)). So in both cases we consider Co-3d states, but the value of U is very different. This is so because Co-3d states require different corrections when they are in different chemical environments (these Co-3d states hybridize differently with ligands in different compounds). If you use an average value of 5.73 eV for both systems, then this value is not a response property of any of these systems (I do not know what it is in this case). One can also see DFT+U as DFT with a Hubbard functional: the U correction is different for different systems (why should it be the same?). It's like hybrids: people tune the value of alpha in PBE0 for each system (alpha is related to the inverse of the dielectric constant), and alpha is different for different systems (because the dielectric constant is different). So here is the same, U is different for different systems: different systems need different amount of the corrections to restore the piece-wise linearity of the energy (PRB 71, 035105 (2005)) and alleviate self-interactions. The comparison of energies with different ab initio U values was done in these papers: PRB 99, 094102 (2019); PRR 2, 023313 (2020); PRM 3, 033801 (2019). What should I do in case of complex hull calculations of a phase diagram? I would compute U for each phase and compare energies. With QE it is now possible to calculate the U values for each composition by the hp.x code. Can I compare the resulting total energies with each other safely? Well there is no general consensus on this issue, in part because still many people use empirical U. I think that if U is computed ab initio (i.e. it is really a response property of each material) then it makes sense to compare energies with different U values (U computed for each system). But people are still investigating this issue. I will be happy to hear other opinions, and to hear corrections/remarks if something what I said is misleading. Greetings, Iurii -- Dr. Iurii TIMROV Postdoctoral Researcher STI - IMX - THEOS and NCCR - MARVEL Swiss Federal Institute of Technology Lausanne (EPFL) CH-1015 Lausanne, Switzerland +41 21 69 34 881 http://people.epfl.ch/265334 From: users on behalf of Giuseppe Mattioli Sent: Thursday, October 29, 2020 3:52:48 PM To: Quantum ESPRESSO users Forum Subject: Re: [QE-users] Thermodynamics with DFT+U Dear Malte I suppose that, as a trivial rule of thumb, if U values are not so different then you can use some average value for all systems. HTH Giuseppe Quoting Malte Sachs : Dear all, I read many times in papers that I should not compare total energies of DFT+U calculations with different U values. What should I do in case of complex hull calculations of a phase diagram? With QE it is now possible to calculate the U values for each composition by the hp.x code. Can I compare the resulting total energies with each other safely? Best regards, Malte -- Malte Sachs Anorganische Chemie, Fluorchemie Philipps-Universität Marburg Hans-Meerwein-Straße 4 35032 Marburg (Paketpost: 35043 Marburg) Tel.: +49 (0)6421 28 - 25 68 0 http://www.uni-marburg.de/fb15/ag-kraus/ GIUSEPPE MATTIOLI CNR - ISTITUTO DI STRUTTURA DELLA MATERIA Via Salaria Km 29,3
Re: [QE-users] Thermodynamics with DFT+U
Dear Malte, This is not an easy question. Let me express my opinion. > I read many times in papers that I should not compare total energies of > DFT+U calculations with different U values. Can you give some references please? Well the problem is that in literature often people still use empirical values of U. In this case, I agree that the comparison of energies will depend strongly on U which one chooses based on some arguments. But if one computes U from first principles, then U is a response property of each system (and the response is different in each system, hence different U) then it makes sense to me to compare energies (but I am not aware of any theoretical proof that it is allowed to do so). For example, in LiCoO2 the computed value of U for Co-3d is 6.91 eV, while U for Co-3d in CoO is 4.55 eV (both using 'atomic' orbitals and some pseudos on top of PBEsol - see PRB 101, 064305 (2020)). So in both cases we consider Co-3d states, but the value of U is very different. This is so because Co-3d states require different corrections when they are in different chemical environments (these Co-3d states hybridize differently with ligands in different compounds). If you use an average value of 5.73 eV for both systems, then this value is not a response property of any of these systems (I do not know what it is in this case). One can also see DFT+U as DFT with a Hubbard functional: the U correction is different for different systems (why should it be the same?). It's like hybrids: people tune the value of alpha in PBE0 for each system (alpha is related to the inverse of the dielectric constant), and alpha is different for different systems (because the dielectric constant is different). So here is the same, U is different for different systems: different systems need different amount of the corrections to restore the piece-wise linearity of the energy (PRB 71, 035105 (2005)) and alleviate self-interactions. The comparison of energies with different ab initio U values was done in these papers: PRB 99, 094102 (2019); PRR 2, 023313 (2020); PRM 3, 033801 (2019). > What should I do in case of complex hull calculations of a phase diagram? I would compute U for each phase and compare energies. > With QE it is now possible to calculate the U values for each composition by > the hp.x code. Can I compare the resulting total energies with each other safely? Well there is no general consensus on this issue, in part because still many people use empirical U. I think that if U is computed ab initio (i.e. it is really a response property of each material) then it makes sense to compare energies with different U values (U computed for each system). But people are still investigating this issue. I will be happy to hear other opinions, and to hear corrections/remarks if something what I said is misleading. Greetings, Iurii -- Dr. Iurii TIMROV Postdoctoral Researcher STI - IMX - THEOS and NCCR - MARVEL Swiss Federal Institute of Technology Lausanne (EPFL) CH-1015 Lausanne, Switzerland +41 21 69 34 881 http://people.epfl.ch/265334 From: users on behalf of Giuseppe Mattioli Sent: Thursday, October 29, 2020 3:52:48 PM To: Quantum ESPRESSO users Forum Subject: Re: [QE-users] Thermodynamics with DFT+U Dear Malte I suppose that, as a trivial rule of thumb, if U values are not so different then you can use some average value for all systems. HTH Giuseppe Quoting Malte Sachs : > Dear all, > > I read many times in papers that I should not compare total energies > of DFT+U calculations with different U values. What should I do in > case of complex hull calculations of a phase diagram? With QE it is > now possible to calculate the U values for each composition by the > hp.x code. Can I compare the resulting total energies with each > other safely? > > Best regards, > Malte > > -- > Malte Sachs > Anorganische Chemie, Fluorchemie > Philipps-Universität Marburg > Hans-Meerwein-Straße 4 > 35032 Marburg (Paketpost: 35043 Marburg) > Tel.: +49 (0)6421 28 - 25 68 0 > http://www.uni-marburg.de/fb15/ag-kraus/ GIUSEPPE MATTIOLI CNR - ISTITUTO DI STRUTTURA DELLA MATERIA Via Salaria Km 29,300 - C.P. 10 I-00015 - Monterotondo Scalo (RM) Mob (*preferred*) +39 373 7305625 Tel + 39 06 90672342 - Fax +39 06 90672316 E-mail: ___ Quantum ESPRESSO is supported by MaX (www.max-centre.eu<http://www.max-centre.eu>) users mailing list users@lists.quantum-espresso.org https://lists.quantum-espresso.org/mailman/listinfo/users ___ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list users@lists.quantum-espresso.org https://lists.quantum-espresso.org/mailman/listinfo/users
Re: [QE-users] Thermodynamics with DFT+U
Dear Malte I suppose that, as a trivial rule of thumb, if U values are not so different then you can use some average value for all systems. HTH Giuseppe Quoting Malte Sachs : Dear all, I read many times in papers that I should not compare total energies of DFT+U calculations with different U values. What should I do in case of complex hull calculations of a phase diagram? With QE it is now possible to calculate the U values for each composition by the hp.x code. Can I compare the resulting total energies with each other safely? Best regards, Malte -- Malte Sachs Anorganische Chemie, Fluorchemie Philipps-Universität Marburg Hans-Meerwein-Straße 4 35032 Marburg (Paketpost: 35043 Marburg) Tel.: +49 (0)6421 28 - 25 68 0 http://www.uni-marburg.de/fb15/ag-kraus/ GIUSEPPE MATTIOLI CNR - ISTITUTO DI STRUTTURA DELLA MATERIA Via Salaria Km 29,300 - C.P. 10 I-00015 - Monterotondo Scalo (RM) Mob (*preferred*) +39 373 7305625 Tel + 39 06 90672342 - Fax +39 06 90672316 E-mail: ___ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list users@lists.quantum-espresso.org https://lists.quantum-espresso.org/mailman/listinfo/users
[QE-users] Thermodynamics with DFT+U
Dear all, I read many times in papers that I should not compare total energies of DFT+U calculations with different U values. What should I do in case of complex hull calculations of a phase diagram? With QE it is now possible to calculate the U values for each composition by the hp.x code. Can I compare the resulting total energies with each other safely? Best regards, Malte -- Malte Sachs Anorganische Chemie, Fluorchemie Philipps-Universität Marburg Hans-Meerwein-Straße 4 35032 Marburg (Paketpost: 35043 Marburg) Tel.: +49 (0)6421 28 - 25 68 0 http://www.uni-marburg.de/fb15/ag-kraus/ smime.p7s Description: S/MIME Cryptographic Signature ___ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list users@lists.quantum-espresso.org https://lists.quantum-espresso.org/mailman/listinfo/users
