[QE-users] oscillations in G(V) diagrams

[Lorenzo Paulatto]

Hello Jakob,

you do not give much detail about what you are doing. As said, QHA is 
effective when dealing with one degree of freedom (i.e. cubic 
semiconductor) but harder to use in any other case. Are you doing a 
constant-volume variable-cell relax (aka cell_dofree='shape') for a 
series of volumes? And then computing for each volume the Helmholtz free 
energy (from the phonons directly or from the dos)? Are you doing this 
your self by hand or using one of the available QHA software packages?

The oscillations could be an honest bug, or a difficult integration of 
the DOS.

cheers


On 04/11/2022 09:20, Jakob Kraus wrote:
> Dear QE users,
>
>
> I am trying to calculate heat capacities, and to this end, I have 
> calculated the Gibbs energy as a function of volume
>
> at several temperatures in a range of 0-700 K.
>
> However, the functions that result from this do not show a single 
> minimum, but rather a whole lot of oscillations, which
>
> seem to originate from the phonons, since the E(V) diagram at 0 K 
> shows a single minimum as expected.
>
> I am thankful for any help you can offer with getting rid of these 
> oscillations.
>
> I have attached input files and some plots to showcase the problem.
>
>
> Best regards,
>
>
> Jakob Kraus, TU Freiberg
>
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-- 
Dr. Lorenzo Paulatto
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