[Wien] How to obtain the input data of distorted lattice of non-cubic crystal?

[Jian Zhu]

Well-beloved Prof. Blaha,
    Thank you very much for your instruction.
     Best regards.

Yours sincerely,

Jian Zhu


2006/11/30, Peter Blaha <pblaha at theochem.tuwien.ac.at>:
>
> I have not done such calculations myself. So you really must study the
> literature and there are many examples well described (I think there are
> at least papers by Mehl or D.Singh on these topics.)
> >     (1) Which vector should be chosen to be mutiplied with the
> > strain matrix, primitive cell vectors or conventional cell vectors? For
> > the cubic structure,for example the TiC, the primitive cell vector is
> > different with the conventional cell vector. Please give me a clear
> > instruction about this point.
>
> I guess you can do it either way. More convenient is working with
> convential cell.
> >     (2) You said the strain matrix must be in the same system as the
> > bravais matrix. Here, is the bravais matrix is the conventional bravais
> > matrix? Or primitive bravais matrix? Which should be chosen?
> > Furthermore, taking the TiC as an example, the bravais matrix of TiC
> > should be cubic system, but the tetragonal train matrix and the
> > rhombohedral train matrix are chosen in the automatic calculation of
> > elastic constants by wien2k. Why?
>
> I don't understand this question.
> Of course, a certain strain matrix will lead to tetragonal or
> rhombohedral lattices. You cannot stay in cubic symmetry and get an
> information about an uniaxial strain.
>
> >     (3) Comparing with the cartesian coordinates and fractional
> > coordinates of the original structure, will the respective coordinates
> > change of the distorted structure? If they do change, how will they
> > change, respectively?
>
> Again I can't answer this question in a general way. At first they do
> not change, you just rigidly strain the cell.
>
>                                       P.Blaha
> --------------------------------------------------------------------------
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
> Email: blaha at theochem.tuwien.ac.at    WWW:
> http://info.tuwien.ac.at/theochem/
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-- 
Scoool of Materials Science and Engineering
Central South University
Jian Zhu
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