Re: [Phonopy-users] use phonopy-qha

[Atsushi T. <atz...@gm...>]

Hi,

The Helmholtz free energy implemented in phonopy is that defined for
harmonic (or quasi-harmonic) frequencies. So if there are imaginary
modes, it is not well treated. Therefore phonopy-qha gives wrong
result. This problem may be overcome considering anharmonicity
explicitly, but this is beyond the feature of phonopy.

Togo

On Mon, Apr 23, 2012 at 8:06 PM, Dr. Ravi Chinnappan <ra...@ig...> wrote:
> Dear phonopy users,
>
> I am trying use to VASP-DFPT phonopy interface.
>
> The syntax:
>
> phonopy-qha e-v.dat thermal_properties-{1..10}.yaml
>
> It is stated in the manual that the list of "thermal_properties.yaml"
> files corresponds to the respective volumes of e-v.dat file.
>
> The phonon spectrum corresponding to non-equilibrium volumes show
> imaginary bands (which was not there for equilibrium volume).
>
> Whether the calculation is an error?  If so, how to get around this
> error?
>
> Thanks,
> Ravi
>
> --
> Dr. Ravi Chinnappan <ra...@ig...>
> Indira Gandhi Centre for Atomic Research
>
>
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-- 
Atsushi Togo
http://atztogo.users.sourceforge.net/
atz...@gm...