Dear Bob,
--- On Sun, 8/9/09, john Bob <bobjohn.lzu at gmail.com> wrote:
> Do you mean, physical meaning of thermal properties calculation for
> "meta-stable" phase still need to be explored. The
> method?of calculating these is not so simple ?
>
Well, some metastable phases have no problems with phonons, i.e. they have no
imaginary frequences. Diamond is a good example. In this case no problems with
thermal property calculations.
When frequences become imaginary, you will mix Real and Imaginary values, which
seems to be meaningless. Omitting imaginary frequencies and then integrating
of thermal properties one implicitly suppose another, dynamically stable phase.
If you have high temperature phase (like bcc Ti, Zr), you can not avoid
soft modes. In this case anharmonism plays the main role and phonon-phonon
interaction corrects the phonon picture.
?
> as for my third question : the attached picture can explain.
Take more q-points and you will have better quality picture.
Please, your affiliation.
Bests,
Eyvaz.
