Use the following procedure 1. Optimize the lattice parameters (volume, c/a, b/a etc.) 2. Use x mini using the optimized lattice parameters to get the optimized atomic positions 3. Use (i) and (ii) outputs in phonon initialization and use run_phonon
Suddhasattwa _____ From: [email protected] [mailto:wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of Yundi Quan Sent: Friday, September 02, 2011 5:19 AM To: A Mailing list for WIEN2k users Subject: Re: [Wien] phonon calculation When doing structure minimization, I need to calculate a series of structures. Is it fine to set different Muffin-Tin sphere for different calculations. I believe it is fine because I am not comparing them with each other. Is it? Yundi On Thu, Sep 1, 2011 at 12:41 PM, Laurence Marks <L-marks at northwestern.edu> wrote: Yes, much to large. Read the FAQ on minimization, you are doing something wrong. 2011/9/1 Yundi Quan <quanyundi at gmail.com>: > Thanks for you reply. My minimization stops with a message saying that the > force is minimized and the force and energy are inconsistent. So I carried > out another calculation by using the structure file that I got. However, the > force on one of the atoms is as large as 26. Is it too large to be used as a > equilibrium state? > Thanks a lot. > Yundi > > 2011/8/31 ??????? ???????? <evgeniya at theochem.tuwien.ac.at> >> >> I mean minimization of internal parameters (lattice coordinates) in your >> initial structure. This is a crucial point. You should not have forces on >> atoms, since it is a kind of reference state. The structure optimization >> (lattice parameters) itself is less crucial as long as you have the >> reasonable lattice parameters. >> >> Once you have a well relaxed structure, you can construct atomic >> displacements and calculate 'total forces' using force convergence criteria >> (-fc) at fixed lattice constants. >> >> Total forces, which you need for phonon calculations, are the derivatives >> of total energies with respect to atomic displacements. Therefore, in order >> to get more precise values of total forces one usually constructs big >> supercells. This means that a size of your supercell is also important. > > >> >> >> >> 2011/8/31 Yundi Quan <quanyundi at gmail.com> >>> >>> By relaxing structure, do you mean internal structure or the crystal >>> structure or both? >>> >>> Yundi >>> >>> 2011/8/31 ??????? ???????? <evgeniya at theochem.tuwien.ac.at> >>>> >>>> Fisrt you have to relax your structure until you have no forces on all >>>> your atoms. Then you create the displacements and perform scf calculations >>>> without minimization. >>>> >>>> 2011/8/31 Yundi Quan <quanyundi at gmail.com> >>>>> >>>>> Hi, When doing phonon calculation, do I have to do structure >>>>> minimization first? >>>>> Yundi >>>>> _______________________________________________ >>>>> Wien mailing list >>>>> Wien at zeus.theochem.tuwien.ac.at >>>>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >>>>> >>>> >>>> >>>> >>>> -- >>>> Evgeniya Kabliman. >>>> Insitute of Materials Chemistry Vienna University of Technology >>>> Getreidemarkt 9/165-TC, A-1060 Vienna, Austria >>>> Tel: +43 1 58801 15674 <tel:%2B43%201%2058801%2015674> Fax: +43 1 58801 15698 <tel:%2B43%201%2058801%2015698> >>>> evgeniya at theochem.tuwien.ac.at http://www.imc.tuwien.ac.at >>>> >>>> _______________________________________________ >>>> Wien mailing list >>>> Wien at zeus.theochem.tuwien.ac.at >>>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >>>> >>> >>> >>> _______________________________________________ >>> Wien mailing list >>> Wien at zeus.theochem.tuwien.ac.at >>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >>> >> >> >> >> -- >> Evgeniya Kabliman. >> Insitute of Materials Chemistry Vienna University of Technology >> Getreidemarkt 9/165-TC, A-1060 Vienna, Austria >> Tel: +43 <tel:%2B43%201%2058801%2015674> 1 58801 15674 Fax: +43 1 58801 15698 <tel:%2B43%201%2058801%2015698> >> evgeniya at theochem.tuwien.ac.at http://www.imc.tuwien.ac.at >> >> _______________________________________________ >> Wien mailing list >> Wien at zeus.theochem.tuwien.ac.at >> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien >> > > > _______________________________________________ > Wien mailing list > Wien at zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > > -- Laurence Marks Department of Materials Science and Engineering MSE Rm 2036 Cook Hall 2220 N Campus Drive Northwestern University Evanston, IL 60208, USA Tel: (847) 491-3996 <tel:%28847%29%20491-3996> Fax: (847) 491-7820 <tel:%28847%29%20491-7820> email: L-marks at northwestern dot edu Web: www.numis.northwestern.edu Research is to see what everybody else has seen, and to think what nobody else has thought Albert Szent-Gyorgi _______________________________________________ Wien mailing list Wien at zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20110902/0b808197/attachment.htm>
