Dear Lihui,
>?performing calulation of frequency and zero point
> energy of CO2 molecule. However, unfortunately, I have
> obtained?negative frequency.
> there are several possible reseaons:
Well, you did not include one more reason counting them:
there is a physical reason for this as you consider CO2 molecule (the linear
chain). Obviously, its physical properties do not change if you rotate it
fixing C atom in the cell center. This might lead to negative frequencies.
If you like to consider CO2 as a molecule you should use the Gamma point only
(i.e. you consider CO2 in a big box).
> In addition, I intend to calculate the zero point
> energy of system by PHNONS code, but it does not give the
> zero point energy and other thermodynamics properties in
> output file. How could I do? I need your help
> urgently.
PH code itself does not calculate these properties.
You can try download the QHA code from qe-forge.org. If some troubles with
this, please let me know.
> I need your help urgently.
Please keep in mind our forum consists of volunteers and nobody is oblidged to
give you urgent reply.
Bests,
Eyvaz.
P.S. Can you please show eigendisplacements?
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Prof. Eyvaz Isaev,
Theoretical Physics Department, Moscow State Institute of Steel & Alloys,
Russia,
Department of Physics, Chemistry, and Biology (IFM), Linkoping University,
Sweden
Condensed Matter Theory Group, Uppsala University, Sweden
Eyvaz.Isaev at fysik.uu.se, isaev at ifm.liu.se, eyvaz_isaev at yahoo.com
