[Pw_forum] surface embedding method to simulate semi-infinite system
Hi PW developers and users: Recently I found the ?surface embedding method? propused by Inglesfield and Ishida is interesting and maybe powerful. In this method, surfaces are simulated by infinite system instead of slabs with finite number of layers. I found that this method seems to be implemented in LAPW basis. My question is has this method been implemented by PWSCF? Or is there any other free software implementing this method? best wishes, Yun-Peng -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120301/ec4d0351/attachment.htm
[Pw_forum] about PWCOND
Dear Alex: Following the pwcond examples in QE-4.3.2, I calculated the complex bands for 1D aluminum wire and I got the band.re and band.im output files. Because k_x,k_y = 0 is given in input file, so the first column in band.re is the real k_z. But for the first column in band.im, I cannot understand what is the meaning. Any clue? best wishes, Yun-Peng From: Alex Smogunov Sent: Wednesday, February 22, 2012 9:45 PM To: Yunpeng Wang Cc: Forum PWSCF ; alexander.smogunov at cea.fr Subject: Re: [Pw_forum] about PWCOND Dear Yun-Peng. Le 21 f?vrier 2012 14:46, Yunpeng Wang a ?crit : PWscf authors and users: I want to find answers to the following questions about PWCOND because I am new PWCOND user. 1. Does nonequilibrium Greens function employed in PWCOND? PWCOND does not use NEGFs it calculates directly the scattering states in real space. Or, the effective potential in scattering region is self-consistently obtained or from the effective potential from scattering region SCF calculation? It should be run after PW calculations, so it uses the SCF potential of the leads and the scattering region at equilibrium. It is therefore zero bias approach, no finite voltage is implemented yet. best regards, Alexander In my opinion, effective potential is not self-consistently obtained. 2. Is PWCOND applicable to finite-voltage case? In my opinion, it can not. best wishes, Yun-Peng ___ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120223/4e358cd3/attachment.htm
[Pw_forum] query on fermi energy
if we do a bulk calculation, vacuum energy level can not be calculated, because in bulk, there is no vacuum. To calculate vacuum energy level and the relative energies in bulk with respect to vacuum energy level, a slab calculation should be done. In a slab calculation, several layer of materials as well as a vacuum with sufficient thinkness should be included in one unit cell. YP -- From: Ajit Vallabhaneni Sent: Sunday, January 15, 2012 1:06 AM To: PWSCF Forum Subject: Re: [Pw_forum] query on fermi energy Yun-peng, Thanks for your response. Is it possible to know what the vaccum energy level is ? I read in the FAQ that it cannot be calculated from the a bulk calculation alone. Thanks Ajit ___ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum
[Pw_forum] Ewald and Coulomb
Let?s consider positive point charges q in one dimensional lattice, that is, at x=a*j, j=-infinity,...,-2,-1,0,1,2,...,+infinity. In order to calculate the electrostatic energy due to Coulomb interaction between the charge at x=0 and all the other charges, one should calculate the summation: 1/a * sum_j q^2/j. However, the summation is not converged and is positive infinite. In summary, electrostatic interaction energy for charged system is infinite and one needs some other technique to calculate it. Yun-Peng From: jiayudai Sent: Saturday, January 14, 2012 10:17 PM To: pw_forum at pwscf.org Subject: Re: [Pw_forum] Ewald and Coulomb Dear Yun-Peng, Thanks for your explanation. In fact, what i mean is that how to treat the ion-ion interactions with some charges. For example, sometimes we want to take out one or more electrons out of the system, thus the tot_charge in the system is not zero. In an extreme case, all electrons are ionized and taken out, there are only positive ions in the system. In this case, the Ewald potential should not be right but the real Coulomb potential should be correct. Since Ewald scheme considers the screnning by the electrons. Thus, i want to use the exact 1/r potential to represent the Ewald scheme. So, how can we reach this goal? Best wishes. Jiayu >>> what do you mean by "true Coulomb potential"? Based on density functional theory, adding an uniform potential to the system make no difference. In fact, the ion-ion interaction energy is an infinite value because of 1/r type of Coulomb potential. However, if an uniform charge density which makes total charge zero, hence uniform Coulomb potential is added to the system, the electrostatic energy as well as potential is finite, at the same time, physics keep unchanged. best wishes,Yun-Peng Date: Fri, 13 Jan 2012 21:49:59 +0800 From: daiji...@nudt.edu.cn To: pw_forum at pwscf.org Subject: [Pw_forum] Ewald and Coulomb Dear users and developers, Happy new year! I have a confusion about the calculations of ion-ion interactions. We know, we usually use Ewald scheme to represent the real Coulomb potentials in a periodic cell. Generally, it is correct for a neutral system or one electron taken out (or into ) system. However, if the system is constructed with partially charged ions, that is to say, there are more positive charges than negative charges, the Ewald scheme should be not right. Although this system is not stable, but there should be some properties deserved to study. So, how can we calculate the true Coulomb potentials in DFT? That is to say, we do not use Ewald, but only use th 1/r type. I know it can be realized in classical calculations, but i did not find the path to get it in QE. Thanks a lot. Jiayu ___ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120114/b98f04ed/attachment.htm
[Pw_forum] query on fermi energy
for the first question, there is no absolute Fermi energy. The only absolute energy is that substracting vacuum energy level from it. best Yun-Peng -- From: Ajit Vallabhaneni Sent: Saturday, January 14, 2012 3:32 PM To: PWSCF Forum Subject: [Pw_forum] query on fermi energy Dear users, 1. I was wondering how to calculate the absolute value of fermi energy for graphene single layer. By varying the size of the super cell in the out of plane direction, i observed that the total energy is constant indicating no interactions in the out of plane direction, but the fermi energy is varying with increasing distance. I think it is the relative fermi energy which is output after the scf calculation. I want to know the absolute value. 2. Another question i have is regarding the e-ph calculation. For a give set of q and k points, what is the best way to ensure that all k+q points are available to avoid the message " q is not a vector in the dense grid" in the calculations"? I observed that using a dense grid is not enough sometimes. Do we have to check it outside of the quantum espresso before the calculation begins? Thanks Ajit ___ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum
[Pw_forum] atom positions in terms of alat
I am not sure I understand your question clearly. In relax calculation, lattice is not changed and positions of atoms also change unless you explicitly make them fixed. Yun-Peng From: Payam Norouzzadeh Sent: Thursday, January 12, 2012 11:48 PM To: pw_forum at pwscf.org Subject: [Pw_forum] atom positions in terms of alat Dear Q.E users I have a simple question: atom coordinates in terms of alat and after relaxation should be the same for different lattice constants. Regardless of the lattice constant the atom position for atom number 1 in a system should not change. For example, for lattice constants 10 or 12 angstroms it should be 0. 0.5 0.25.It must be scaled.Is that correct? Best regards,Nima Pirouzmand ___ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120112/1584407e/attachment.htm
[Pw_forum] RPA+EXX in PWscf
thanks! once I have response, I will told you and all the members here. Yun-Peng -- From: Axel Kohlmeyer Sent: Thursday, January 12, 2012 10:44 PM To: PWSCF Forum Subject: Re: [Pw_forum] RPA+EXX in PWscf 2012/1/12 Peter Wang : > Hi: > > I found RPA+EXX has been implemented in QE, see this paper: H. Nguyen, et > al., Phys. Rev. B 79, 205114 (2009). However, I found nothing related to > RPA+EXX in manual or examples. My question is, does the RPA+EXX > implementation been released? Which version? Any manual? Any example? you should direct this kind of questions first to the (corresponding) author of the paper, don't you think? axel. > > best wishes, > Yun-Peng > > ___ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > -- Dr. Axel Kohlmeyer akohlmey at gmail.com http://goo.gl/1wk0 College of Science and Technology Temple University, Philadelphia PA, USA. ___ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum
[Pw_forum] RPA+EXX in PWscf
Hi: I found RPA+EXX has been implemented in QE, see this paper: H. Nguyen, et al., Phys. Rev. B 79, 205114 (2009). However, I found nothing related to RPA+EXX in manual or examples. My question is, does the RPA+EXX implementation been released? Which version? Any manual? Any example? best wishes, Yun-Peng -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120112/7cf23261/attachment.htm
[Pw_forum] k-point
k-points are used for integration over BZ which is described in any DFT book. Yun-Peng From: Rahen Badsha Sent: Tuesday, January 10, 2012 1:55 AM To: pw_forum at pwscf.org Cc: pw_forum at pwscf.org Subject: [Pw_forum] k-point Dear All, I am a new user of QE. I have a question. What is meant by k-points in pwscf? Regards, Md. Rahen Badsha (Raihan) A Post Graguate Thesis Student of Rajshahi University, Bangladesh. ___ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120110/f49ecc43/attachment.htm
[Pw_forum] query on k-points with MP
You can give k-points in input file explicitly, that is, you write them one by one. I think this may work. Yun-Peng -- From: Ajit Vallabhaneni Sent: Tuesday, January 10, 2012 7:38 AM To: PWSCF Forum Subject: [Pw_forum] query on k-points with MP Dear users, I am doing some scf calculations with K-points specified by the Monkhorst-Pack grid scheme. In the output file, only the k-points in the IBZ are shown. Is there any way i can see all the K-points in the entire BZ? I just want to make sure certain K points are included. Thanks Ajit ___ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum
[Pw_forum] hybrid functional error
I am sorry I can not get you. Do you recommand me to use PBE0 instead of HSE06? best, Yun-Peng -- From: hannu.ko...@epfl.ch Sent: Sunday, December 18, 2011 10:51 PM To: pw_forum at pwscf.org Subject: Re: [Pw_forum] hybrid functional error Since n is always 1, and by quickly looking at the code it should be that x>=0. Furthermore, x should be zero only if the density gradient is zero and the screening parameter is set to zero (=screening length infinity = PBE0). If you have done so, then you can fix the problem by either using PBE0 or using a very small parameter value (btw., these two approaches give slightly different results, although they should give the same). If you haven't done so, then... ? Hannu-Pekka Komsa University of Helsinki > >> from expint : error # 1 >> bad arguments >> >> Where is the problem? > > it is where the error message says it is: in "expint" (flib/expint.f90). > If you go inside the file, you will see that this error arises when >* n < 0 , or >* n=0,1 and x<=0, or >* n>1 and x<0 > The second case is the relevant one, I guess, > Please specify which version of QE you are using: there have been > several minor changes to the HSE routines since the first release. > ___ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum
[Pw_forum] hybrid functional error
Hi PG: I am using QE version 4.3.2 and my system is spin-polarized. Yun-Peng -- From: Paolo Giannozzi Sent: Saturday, December 17, 2011 7:42 PM To: PWSCF Forum Subject: Re: [Pw_forum] hybrid functional error On Dec 17, 2011, at 12:40 , Paolo Giannozzi wrote: > Please specify which version of QE you are using: there have been > several minor changes to the HSE routines since the first release. and also please specify if your calculation is spin-polarized or not. P. --- Paolo Giannozzi, Dept of Chemistry&Physics&Environment, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222 ___ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum
