[Wien] Calculations at moderate T

Laurence Marks L-marks at northwestern.edu
Wed Apr 10 01:50:16 CEST 2013

Thanks. Method a) is the only reasonable one, coupled with
extrapolating the bulk reference lattice parameters. This would have
to be done by a uniform volume expansion without relaxation of course.

On Tue, Apr 9, 2013 at 3:03 PM, Peter Blaha
<pblaha at theochem.tuwien.ac.at> wrote:
> a) Simply empirically extrapolate a0 to a possible value at 1200 K.
> b) Ab initio: quasiharmonic approximation.
>     Calculate phonons (wien2k + ponon or phonopy, see u supported sw)
>     and resulting -TS at various lattice parameters and
>     search for the minimum of the free energy as function of a0
>     at the desired T
> Of course, for a surface this is more difficult. Of course one can use the
> expanded a,b lattice constants, but relaxation of z will still corrsepond
> to t=0. It is more a simulation of an epitactically expanded lattice.
> Am 09.04.2013 19:38, schrieb Laurence Marks:
>> Does anyone know of methods to do calculations at T~1200K taking
>> account of bulk thermal expansion? I am interested in a surface
>> calculation where I suspect that it may be important to consider this,
>> and a moderately rational approach to doing this that has been
>> tested/published would be useful.
> --
> -----------------------------------------
> Peter Blaha
> Inst. Materials Chemistry, TU Vienna
> Getreidemarkt 9, A-1060 Vienna, Austria
> Tel: +43-1-5880115671
> Fax: +43-1-5880115698
> email: pblaha at theochem.tuwien.ac.at
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Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu 1-847-491-3996
"Research is to see what everybody else has seen, and to think what
nobody else has thought"
Albert Szent-Gyorgi

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