[Wien] Volume optimization

[Ali Baghizhadeh]

Thank you Prof. Blaha

It takes a bit of time, but at least I will understand either shrinkage or expansion of lattice is more energetically favorable.

Best regards

Ali

________________________________
From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> on behalf of Peter Blaha <pblaha at theochem.tuwien.ac.at>
Sent: 04 February 2020 15:20:20
To: wien at zeus.theochem.tuwien.ac.at
Subject: Re: [Wien] Volume optimization

I'd guess you have experimental "a" lattice constants and in epitaxial
growth you want to optimize  "c"  ??? Otherwise it does not work for
hexagonal symmetry.

It is a very difficult task: You have to edit case.struct yourself and
change c, run a scf cycle and save.
Make another change and run another scf cycle.

Compare the energies and calculate yourself the optimal "c".

There is no "click + core-dump" button for a 1D optimization.

On 2/4/20 12:18 PM, Ali Baghizhadeh wrote:
> Dear Wien2k users
>
> I am working on a hexagonal structure of YMnO3 epitaxial thin film. I
> have experimental c-constant for different substrates, and I like to
> estimate a-constant from DFT (assuming a unit cell similar to bulk one).
> Looking at Optimize option, I could not figure out how to fix “c” and
> relax “a”. Seems I can either optimize volume or c/a ratio or both, not
> c or a alone. Is there any way to proceed with this calculation? Would
> it be more rational if I relax atomic positions first, with experimental
> c-constant and theoretical a-constant?
>
> Thank you in advance
>
> Ali
>
>
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--

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
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