[Wien] [SPAM?] structure relaxation query for phonopy calculations

[Stefaan Cottenier]

Using run_lapw -fc 0.1 is fine. The -fc does not mean that positions will be optimized. It means that at the end of the scf cycle full forces will be calculated, and forces is what you want to know in a phonon calculation.

You must not use min_lapw or run_lapw -min, as these will optimize the positions of atoms (and hence will bring back your displaced atoms to their original positions, where the forces are zero).

Stefaan


Van: Wien [mailto:wien-bounces at zeus.theochem.tuwien.ac.at] Namens chin Sabsu
Verzonden: donderdag 25 januari 2018 18:19
Aan: A. Mailing List for WIEN2k Users <wien at zeus.theochem.tuwien.ac.at>
Onderwerp: [Wien] [SPAM?] structure relaxation query for phonopy calculations

Dear Sir,

In one of the Phonopy exercise for  SrTiO3, Peter Sir mentioned the "run_lapw -fc 0.1" command to run scf for Phonopy generated structure files.

My query is: without min_lapw switch, does "-fc0.1" switch will work? If it works then how it will affect the scf calculations?

If my case if SrTiO3 and I am getting three new structure files with Phonopy then do I need to do scf calculation

with "min_lapw -j "run_lapw -fc 0.1 ...." or  simply with "run_lapw -fc 0.1"?


I see in case of SrTiO3 all three generated structure is having high atomic positions but in one my other case the newly generated structures are having some flexible positions (see below part of structure file) so I am not sure how to proceed for scf.


My doubt arises as I read a statement in Phonopy UG .Below is statement which I am not getting well.

"Note  that supercells with displacements must not be relaxed in the force calculations because atomic forces induced  by a small atomic displacement are what we need for phonon calculation."

=== part of struct file =====

ATOM   9: X=0.24520000 Y=0.00000000 Z=0.00000000
          MULT= 6          ISPLIT=-2
ATOM   9: X=0.75480000 Y=0.00000000 Z=0.00000000
ATOM   9: X=0.00000000 Y=0.24520000 Z=0.00000000
ATOM   9: X=0.00000000 Y=0.75480000 Z=0.00000000
ATOM   9: X=0.00000000 Y=0.00000000 Z=0.24520000
ATOM   9: X=0.00000000 Y=0.00000000 Z=0.75480000
I          NPT=  781  R0=0.00001000 RMT=    2.5000   Z: 53.0
LOCAL ROT MATRIX:    0.0000000 0.0000000 1.0000000
                     0.0000000 1.0000000 0.0000000
                    -1.0000000 0.0000000 0.0000000
ATOM  10: X=0.74520000 Y=0.50000000 Z=0.00000000
          MULT= 6          ISPLIT=-2
ATOM  10: X=0.25480000 Y=0.50000000 Z=0.00000000
ATOM  10: X=0.50000000 Y=0.74520000 Z=0.00000000
ATOM  10: X=0.50000000 Y=0.25480000 Z=0.00000000
ATOM  10: X=0.50000000 Y=0.50000000 Z=0.24520000
ATOM  10: X=0.50000000 Y=0.50000000 Z=0.75480000
I          NPT=  781  R0=0.00001000 RMT=    2.5000   Z: 53.0
LOCAL ROT MATRIX:    0.0000000 0.0000000 1.0000000
                     0.0000000 1.0000000 0.0000000
                    -1.0000000 0.0000000 0.0000000
ATOM  11: X=0.74520000 Y=0.00000000 Z=0.50000000
          MULT= 6          ISPLIT=-2
ATOM  11: X=0.25480000 Y=0.00000000 Z=0.50000000
ATOM  11: X=0.50000000 Y=0.24520000 Z=0.50000000
ATOM  11: X=0.50000000 Y=0.75480000 Z=0.50000000
ATOM  11: X=0.50000000 Y=0.00000000 Z=0.74520000
ATOM  11: X=0.50000000 Y=0.00000000 Z=0.25480000
I          NPT=  781  R0=0.00001000 RMT=    2.5000   Z: 53.0
LOCAL ROT MATRIX:    0.0000000 0.0000000 1.0000000
                     0.0000000 1.0000000 0.0000000
                    -1.0000000 0.0000000 0.0000000
ATOM  12: X=0.24520000 Y=0.50000000 Z=0.50000000
          MULT= 6          ISPLIT=-2
ATOM  12: X=0.75480000 Y=0.50000000 Z=0.50000000
ATOM  12: X=0.00000000 Y=0.74520000 Z=0.50000000

As the phonon calculations are time demanding so I will start the calculations after getting a response from you!!!


Thanks in advance!!


Chin S.




-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20180125/02a64293/attachment.html>