Re: [Phonopy-users] DFPT and finite difference method

[Aldo H. R. <ar...@qr...>]

are you sure this is correct? the band structure looks to me exactly the
same, no even negative frequencies, while in your DFPT, you have a large
number of negative frequencies.... ummm... check your calculations... that
does not make sense... you can even compare the forces directly...you
should see if there is one that is off..


-> Dear Dr Aldo,
->
->                    As you mentioned, I am providing some details of the
-> calculation:
->
-> My band.conf and mesh.conf files are ATTACHED. The structure I was working
-> on was a Fe2P type hexagonal structure. The system is magnetic. Before
-> starting the phonon calculation, the structure was properly relaxed with
-> EDIFF= 10^-10 and EDIFFG = -0.00001. I am also giving the INCAR's for DFPT
-> and finite displacement method.
->
-------------------DFPT---------------------------------------------------------------------------------
->
->    PREC = Accurate
->
->  IBRION = 8
->
->   EDIFF = 1.0e-10
->
->  MAGMOM = 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3
-> 3
-> 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
-> 1
-> 1
->
->  ISTART = 0
->
->   ENCUT = 500
->
->  ISMEAR = 1
->
->   SIGMA = 0.02
->
->   ISPIN = 2
->
->    NELM = 500
->
-> ADDGRID = .TRUE.
->
->   LREAL = .TRUE.
->
->   LWAVE = .FALSE.
->
->  LCHARG = .FALSE.
->
->  LORBIT = 11
->
-> ---------------------------------------------------------------------
->
->
-> ---------------------Finite
->
Difference-------------------------------------------------------------------------
->
->    PREC = Accurate
->
->  IBRION = -1
->
->   EDIFF = 1.0e-10
->
->  MAGMOM = 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3
-> 3
-> 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
-> 1
-> 1
->
->  ISTART = 0
->
->   ENCUT = 500
->
->  ISMEAR = 1
->
->   SIGMA = 0.02
->
->   ISPIN = 2
->
->    NELM = 500
->
-> ADDGRID = .TRUE.
->
->   LREAL = .TRUE.
->
->   LWAVE = .FALSE.
->
->  LCHARG = .FALSE.
->
->  LORBIT = 11
->
-> ---------------------------------------------------------------------
-> I Used a 2x2x2 supercell for my purpose in both set of calculations.
-> Phonopy created 18 POSCARS s for finite difference method. I also like to
-> attach the band structures and DOS and thermal properties for both sets.
-> Please find the attachment.
->
-> I used the following commands:
-> 1. For band structure in DFPT:
->
->       phonopy --dim="2 2 2" c POSCAR-unitcell band.conf
->
-> 2. For DOS in DFPT:
->
->       phonopy --dim="2 2 2" --readfc -p mesh.conf
->
-> 3. Dor thermal properties:
->
->       phonopy --dim="2 2 2" --readfc -p -t mesh.conf
->
-> Waiting for your response. Thank you very much in advance.
->
-> With kind regards
->
->
-> Prasenjit Roy
-> Electronic Structures of Materials
-> Radboud University
-> Nijmegen
-> +31 (0) 24 36 52805
->
->
-> On Wed, Apr 30, 2014 at 1:52 PM, Aldo Humberto Romero <
-> ar...@qr...> wrote:
->
->> You do not provide any real info that is of help. It could be due to
->> several reasons... due to the size of the atomic displacements in the
->> frozen core, lack of convergence, etc.... it is hard to address this
->> with
->> much.
->>
->> Best
->>
->> -aldo.
->>
->>
->> -> Hi Phonopy users and Dr. Togo,
->> ->
->> ->               I am a very new Phonopy user and do not have much
->> experience
->> -> with it. I wanted to compare the results obtained from Phonopy finite
->> -> displacement method, and VASP-DFPT method. I used the same initial
->> POSCAR
->> -> and performed the calculation with both cases.
->> ->               Then I plotted the band structure from both calculation
->> -> using
->> -> same band.conf. I obtained exactly same bands. But then I plotted DOS
->> and
->> -> thermal properties, using same mesh.conf ( with a "FORCE_CONSTANTS =
->> READ"
->> -> tag in DFPT). Results from finite difference and dfpt are very
->> different.
->> -> To be more specific, the DOS from DFPT is not correct. What is the
->> reason
->> -> behind it, and how to correct it?
->> ->               Kindly help me solve this problem. Thank you very much
->> i
->> -> advance.
->> -> With kind regards,
->> -> Prasenjit Roy
->> -> Electronic Structures of Materials
->> -> Radboud University
->> -> Nijmegen
->> -> +31 (0) 24 36 52805
->> ->
->>
->>
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->>
->> --
->>
->> Prof. Aldo Humberto Romero
->> CINVESTAV-Unidad Queretaro
->> Libramiento Norponiente 2000
->> CP 76230, Queretaro, QRO, Mexico
->> tel: 442 211 9909
->> fax: 442 211 9938
->>
->> email: ar...@qr...
->>         ald...@gm...
->> www: qro.cinvestav.mx/~aromero
->>
->


-- 

Prof. Aldo Humberto Romero
CINVESTAV-Unidad Queretaro
Libramiento Norponiente 2000
CP 76230, Queretaro, QRO, Mexico
tel: 442 211 9909
fax: 442 211 9938

email: ar...@qr...
        ald...@gm...
www: qro.cinvestav.mx/~aromero