[Wien] Size of Supercell, Interaction Range--->Coordination Shell in Phonon

[Peter Blaha]

You don't need "InteractionRange-àCoordination Shell"

Just use "Interaction Range-àSupercell Size"

And of course you define a diagonal matrix with 3,2,1 in the diagonal.

PS: Good phonon dispersions require usually MORE than 36 atoms !!!
PPS: negative (or better imaginary!) dispersions can also come from RKmax.
      Test it with a relatively small cell and check when your phonons at
      the "exact" points (like Gamma or X) are converged.

Am 10.03.2011 10:14, schrieb Ghosh SUDDHASATTWA:
> Dear Wien2k users,
>
> I have been getting all negative dispersion curves for an orthorhombic supercell (12 atom, 18 atom both, 24 atom)
>
> Now I have taken a 3x2x1 supercell (36 atoms) {since the z lattice parameter is 8.2 A)
>
> Although, this question is not directly related to Wien2k, I request all users who are doing phonon calculations
>
> In phonon software, we carry out the following for the creation of the d45 file
>
>    1. Define the lattice parameters (optimized before by Wien2k) (I am using Pnma_51 space group)
>    2. Define the number of displacive particles(non-equivalent atoms etc.)
>    3. Define the coordinates of the displacive particles
>    4. Then we have
>          1. InteractionRange-àCoordination Shell
>          2. Interaction Range-àSupercell Size (Restore symmetry or not, +/- displacements or not etc.)
>
> Now in (a), the default is 1. How do we choose this number. Does the d45 file change if we change this number
>
> With Pnma as space group and three in-equivalent atoms, what should I put for a 3x2x1 supercell
>
> Thanks in advance
>
> Suddhasattwa
>
>
>
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-- 

                                       P.Blaha
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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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