[Wien] phonon calculation

[Евгения Каблиман]

I mean minimization of internal parameters (lattice coordinates) in your
initial structure. This is a crucial point. You should not have forces on
atoms, since it is a kind of reference state. The structure optimization
(lattice parameters) itself is less crucial as long as you have the
reasonable lattice parameters.

Once you have a well relaxed structure, you can construct atomic
displacements and calculate 'total forces' using force convergence criteria
(-fc) at fixed lattice constants.

Total forces, which you need for phonon calculations, are the derivatives of
total energies with respect to atomic displacements. Therefore, in order to
get more precise values of total forces one usually constructs big
supercells. This means that a size of your supercell is also important.


2011/8/31 Yundi Quan <quanyundi at gmail.com>

> By relaxing structure, do you mean internal structure or the crystal
> structure or both?
>
> Yundi
>
>
> 2011/8/31 Евгения Каблиман <evgeniya at theochem.tuwien.ac.at>
>
>> Fisrt you have to relax your structure until you have no forces on all
>> your atoms. Then you create the displacements and perform scf calculations
>> without minimization.
>>
>> 2011/8/31 Yundi Quan <quanyundi at gmail.com>
>>
>>> Hi, When doing phonon calculation, do I have to do structure minimization
>>> first?
>>>
>>> Yundi
>>>
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>>
>>
>> --
>> Evgeniya Kabliman.
>> Insitute of Materials Chemistry         Vienna University of Technology
>> Getreidemarkt 9/165-TC, A-1060 Vienna, Austria
>> Tel: +43 1 58801 15674        Fax: +43 1 58801 15698
>> evgeniya at theochem.tuwien.ac.at          http://www.imc.tuwien.ac.at
>>
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>
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-- 
Evgeniya Kabliman.
Insitute of Materials Chemistry         Vienna University of Technology
Getreidemarkt 9/165-TC, A-1060 Vienna, Austria
Tel: +43 1 58801 15674        Fax: +43 1 58801 15698
evgeniya at theochem.tuwien.ac.at          http://www.imc.tuwien.ac.at
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