Re: [Wien] A basic question regarding using GGA+U approach
Hmm. Depending on the metal, a hybrid DFT calculation for the metal is as problematic (or even more) that a LDA+U calculation. It overestimates itinerant magnetic moments and in addition also affects the "free-electron" like 4s electrons ... Formation energies (voltages) with correlated electrons are always "tricky". I think Ceder has published a lot of such calculations on voltages including various more or less empirical "tricks". Eventually, you may try a meta-GGA ., but this is probably also not very good. Best regards Peter Blaha Am 2/11/22 um 08:19 schrieb xavier rocquefelte: Dear Shamik, To my point of view using the strategy (1) is not correct. I understand that B will require a different treatment in ABS2 and pure B phases. You certainly has no other choice than using hybrid functional for all calculations ... and then you will be able to compare to the results of strategy (2). Best Regards Xavier On 11/02/2022 06:40, shamik chakrabarti wrote: Dear Wien2k users, I have studied the intercalation of A in BS2 to form ABS2. In this calculation, I have used Hubbard U for B in BS2, and in ABS2 & I got reasonable voltage. However, now I want to study the voltage corresponding to the conversion reaction; ABS2 + A =2A2S +B. In this case, B is a metal & hence to simulate the voltage (1) Should I need to consider the energy value corresponding to GGA+U approach applied to ABS2 or, (2) Should I need to consider the energy value corresponding to GGA approach applied to ABS2 As A & A2S & B have been simulated using GGA. Looking forward to your reply in this regard. with regards, -- Dr. Shamik Chakrabarti Research Fellow Department of Physics Indian Institute of Technology Patna Bihta-801103 Patna Bihar, India ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at:http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html -- Professeur des Universités de Rennes 1 Institut des Sciences Chimiques de Rennes (ISCR) Univ Rennes - CNRS - UMR6226, France https://iscr.univ-rennes1.fr/xavier-rocquefelte ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html -- Peter Blaha, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna Phone: +43-1-58801-165300 Email: peter.bl...@tuwien.ac.at WWW: http://www.imc.tuwien.ac WIEN2k: http://www.wien2k.at ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
Re: [Wien] A basic question regarding using GGA+U approach
Dear Prof. Xavier, . . . . . . . . . Thank you for your reply. I will follow your advice & go for hybrid calculation for all. With regards, On Fri, Feb 11, 2022, 12:49 xavier rocquefelte < xavier.rocquefe...@univ-rennes1.fr> wrote: > Dear Shamik, > > To my point of view using the strategy (1) is not correct. I understand > that B will require a different treatment in ABS2 and pure B phases. > > You certainly has no other choice than using hybrid functional for all > calculations ... and then you will be able to compare to the results of > strategy (2). > > Best Regards > > Xavier > > > > On 11/02/2022 06:40, shamik chakrabarti wrote: > > Dear Wien2k users, > >I have studied the intercalation of A in BS2 to > form ABS2. In this calculation, I have used Hubbard U for B in BS2, and in > ABS2 & I got reasonable voltage. > However, now I want to study the voltage corresponding to the conversion > reaction; ABS2 + A =2A2S +B. In this case, B is a metal & hence to simulate > the voltage > (1) Should I need to consider the energy value corresponding to GGA+U > approach applied to ABS2 or, > (2) Should I need to consider the energy value corresponding to GGA > approach applied to ABS2 > > As A & A2S & B have been simulated using GGA. > > Looking forward to your reply in this regard. > > with regards, > > -- > Dr. Shamik Chakrabarti > Research Fellow > Department of Physics > Indian Institute of Technology Patna > Bihta-801103 > Patna > Bihar, India > > ___ > Wien mailing > listw...@zeus.theochem.tuwien.ac.athttp://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > SEARCH the MAILING-LIST at: > http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html > > -- > > Professeur des Universités de Rennes 1 > Institut des Sciences Chimiques de Rennes (ISCR) > Univ Rennes - CNRS - UMR6226, > Francehttps://iscr.univ-rennes1.fr/xavier-rocquefelte > > > ___ > Wien mailing list > Wien@zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > SEARCH the MAILING-LIST at: > http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html > ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
[Wien] A basic question regarding using GGA+U approach
Dear Wien2k users, I have studied the intercalation of A in BS2 to form ABS2. In this calculation, I have used Hubbard U for B in BS2, and in ABS2 & I got reasonable voltage. However, now I want to study the voltage corresponding to the conversion reaction; ABS2 + A =2A2S +B. In this case, B is a metal & hence to simulate the voltage (1) Should I need to consider the energy value corresponding to GGA+U approach applied to ABS2 or, (2) Should I need to consider the energy value corresponding to GGA approach applied to ABS2 As A & A2S & B have been simulated using GGA. Looking forward to your reply in this regard. with regards, -- Dr. Shamik Chakrabarti Research Fellow Department of Physics Indian Institute of Technology Patna Bihta-801103 Patna Bihar, India ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
Re: [Wien] How much computer CPU usage will be required for say a 60 atom model to run. So we want CPU requirements versus the number of atoms for Wein2k
Hi, This question is not so easy to answer, since it is not so clear what kind of HPC you would "rent" (But even 2000 hours is "very little/nearly nothing"). A 60 atom cell (with "complicated atoms, LDA+U, ...") can still be run on a modern PC with 8 cores and 64 (better 128) GB RAM. A single scf calculation may take 1-10 h on this PC. Of course such calculations run faster, when you couple a few PCs (or nodes on a HPC) together and let them work in parallel. Much more difficult is to estimate how many such scf cycles you will have to run. This depends a lot on your skills and what you actually want to calculate. Certainly, phase transitions, entropy, ... require MANY such calculations (100 to a few 1000 ?). There is no "input switch: "Phase transition" or "entropy", you have to set up models, calculate them and derive from the results (total energies) your information. It requires quite some expertise ! I don't know what they would charge you for 2000 h on a HPC cluster, but this is just the cpu time you get from a single PC (costs 2000 US$) in 3 month. Unless you get "very good prices" (nearly for free), renting CPU hours is usually quite expensive as compared to buying your own small cluster, in particular when you go with standard PCs and not with a rack solution based on Xeon processors. The drawback is, that you need to be able to administer the Linux installation (including network and NFS setup, ...) For this project, I'd probably buy 4 - 8 PCs (or more, I don't know how much money you have) (latest Intel I7 or I9 processors (or whatever the numbers are now) with 8 cores, 128 GB RAM) and a good Gbit switch (unless your University provides a good network anyway). Such a cluster can then run for a couple of years (at least the life of a PhD student) providing you with more than 10 cpu-h. HPC systems really are needed only if you go to systems with more than 100-500 atoms/cell, where one MUST use highly parallel mpi jobs, which need several nodes and a Infiniband network. It is a waist of HPC ressources, when you use just one node of such a cluster. A single node on a HPC system is NOT faster than a modern PC !!! Hope this helps. Peter Blaha Am 10.02.2022 um 10:22 schrieb Mohammed S. Mohammed: _<#_msocom_1>Dear Wien2kMailing list users In Egypt we are about to invest some money from a project fund to *Buy or Rent *a high performance computer to calculate the magnetic, electronic, elastic, and magnetocaloricproperties of selected rare-earth transition metal compounds to include R_2 Fe_14 B, Nd_3 Co_11 B_4 .The problem is we have to state in our request for this fund how much computerCPU usage will be required for say a 60-atom model to run. Therefore, we wantCPU requirements versus the number of atoms for Wein2k. Also need to estimatehow many times these models will need to be executed to perform the field,temperature ranges, first and second order phase transitions, magnetization, specificheat, entropy, and MCE properties i.e. the isothermal change in entropy and theadiabatic change in temperature in a wide range of magnetic fields and in atemperature range up to the Curie temperature of the studied systems. I am not sure that we can estimate the number of flops; so far, I have not seen this type of information on the internet for wien2k. There are tools, but not clear, if there has been a paper on the subject. The issue I see is that we need to estimate how much computer time to ask for, so if we can get an estimate that would be a good idea. If they give us, 200 or 2000 hours will that, be enough to do what we want? How much computer time/gflops do we ask for? Thank you foryour patience. Dr / Mohammed Said M. Abu-Elmagd Ph.D. in TheoreticalPhysics /Department of//Physics, Higher Institute of Engineering, Shourok Academy, Cairo, Egypt./ ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at:http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html -- --- Peter Blaha, Inst. f. Materials Chemistry, TU Vienna, A-1060 Vienna Phone: +43-158801165300 Email:peter.bl...@tuwien.ac.at WWW:http://www.imc.tuwien.ac.at WIEN2k:http://www.wien2k.at - ___ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
