questions on phonon calculation and application on relativistic QM system.

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luke419 · #1 Post by **luke419** » Fri Mar 26, 2010 12:23 pm

I'd like to know phonon calculation using VASP as follows.

1. Is it available in VASP 4.6?

2. What should I do for it in detail?

3. What is the name of output file for phonon calculation?
Can I redo the phonon calculation if the job is stopped abnonrally during the running(I use VASP on parallel computer)?

4. It seems that common QM software is coded based on nonrelativistic quantum mechanics.
In case that relativistic quantum mechanics (quantum electrodynamics, QED) should be applied as such in grephene, will there be any fault in VASP to this case?
Would the most of results be valid?
How should we treat the results of VASP for it? If any, for what should we take a care in VASP?

With best regards,

Luke

#2 Post by **admin** » Fri Mar 26, 2010 1:16 pm

you can calculate the Gamma-point phonons with vasp.4.6, using a frozen phonon approach
please use IBRION=5 in that case, and set POTIM = 0.015 (as the harmonic limit is assumed)
in case you do not need all modes, please use the Selective dymanics key in POSCAR and just allow the vibrations you are intrested in (by setting F/T ) in order to save CPU time. it is not possible to continue a broken phonon job (keeping the info) it has to be restarted from the beginning.
relativistic effects can be simulated by using spin-orbit splitting (please have a look at the LSORBIT tag, and the additional parameters you have to set.

boris · #3 Post by **boris** » Fri Mar 26, 2010 4:04 pm

And does IBRION=7 or 8 allow to calculate other phonons than the Gamma point phonons?