My Community

hi,

For some calculations I want to run I need to have the phonon density of state first. Is it possible to obtain this from VASP calculations? I know there is the IBRION=5 option to get frequencies, but is the phonon density of states also generated in VASP5.X, and if so, what are the ec-xtra INCAR parameters. If not, are there any hints on how I could do this myself based on the results obtained in VASP calculations?

Cheers
Danny

VASP can provide you with the dynamical matrix at the gamma point either by finite differences or by DFPT (in VASP5).

To get phonon-DOS you can for example use the free phonopy software (http://phonopy.sourceforge.net/ ). It reads the dynamical matrix either from the OUTCAR file or the vasprun.xml file. It can also provide the phonon bandstructure, atomic projected DOS and the vibrational free energy. In addition there is support for a quasi-harmonic approximation analysis of the data. I haven't used all the functionalities yet but it seems promising.

Hope this helps,

Cheers
/Dan


<span class='smallblacktext'>[ Edited Thu Apr 15 2010, 03:12PM ]</span>

Wow, that sounds really useful, but when I clicked on the link the project it was not there, and I got a server error.

The link as it stood in my above post contained a paranthesis at the end. I have updated it, so please try again.

http://phonopy.sourceforge.net/

<span class='smallblacktext'>[ Edited Thu Apr 15 2010, 03:14PM ]</span>

Thank you for your answer forsdan

I tested the software and it works perfectly.

Regards

thx forsdan. I have just downloaded and installed it (without a glitch, which is to my experience quite unique in the linux world ) It also looks quite decent.

After having read having read through the manual and some extra tutorials on phonon calculations, I might however also put in the effort to write something myself.

Cheers
Danny

thanks, that worked I am going to try it out now!

Sounds like a neat program. I am also trying to install it, it works immediately when you have Ubuntu, but it is still not easy to install if you don't have Ubuntu.

Yes, it seems that it is especially designed for Debian systems.

I installed the phonopy software and tried few examples given in the phonopy folder. Everything worked fine.

Then I tried to use one of my own examples. I used a system of 5 atoms per unit cell. I prepared a 2 by 2 by 1 supercell and used the POSCAR to generate phono modes in Vasp with IBRION = 5 ( I do not have Vasp 5.2 so I could not try IBRION = 8 ) with POTIM = 0.01 and NFREE = 2. I got the DYNMAT and phonon modes for 15 displacements.

Then from the DYNMAT of Vasp I prepared the "FORCES" file for phonopy according to its format. Then I generated anime.ascii and band.yaml files in phonopy. It worked fine. I got the files. I can also open anime.ascii with v_sim and see the phonon modes.

But the problem is:

The frequency for the phonon modes given by phonopy do not look
right. Some of those are negative and the results do not match at all with the Vasp results at the Gamma point. Am I doing something wrong? Can anybody help me sort out this issue?

Many thanks for the help.

Best regards,
Ferdows


Here are the relevant files:

INPHON
---------

NDIM = 1 1 1
ATOM_NAME = Te Bi
PRIMITIVE_AXIS = 0.5 0 0 0 0.5 0 0 0 1
ANIME = 0.0 0.0 0.0


POSCAR (for phonpy without selective dynamics option)
--------------------------------------------------------


SYSTEM: Bi2Te3 bulk vibration 2 by 2 by 1 supercell
1.000
7.707188205240295 4.187106074597922 19.68315992116976
0 8.771123491943904 19.68315992116976
0 0 10.7744998931885
12 8
direct
0.00000 0.00000 -0.00000
0.00000 0.50000 0.00000
0.50000 -0.00000 -0.00000
0.50000 0.50000 0.00000
0.10600 0.10600 0.21200
0.10600 0.60600 0.21200
0.60600 0.10600 0.21200
0.60600 0.60600 0.21200
0.39400 0.39400 0.78800
0.39400 0.89400 0.78800
0.89400 0.39400 0.78800
0.89400 0.89400 0.78800
0.20000 0.20000 0.40000
0.20000 0.70000 0.40000
0.70000 0.20000 0.40000
0.70000 0.70000 0.40000
0.30000 0.30000 0.60000
0.30000 0.80000 0.60000
0.80000 0.30000 0.60000
0.80000 0.80000 0.60000

Please direct your question to the phonopy mailing-list

https://lists.sourceforge.net/lists/lis ... nopy-users

Cheers,
/Dan