[Wien] Doubts regarding the volume optimization of a triclinic cell

[Dr. K. C. Bhamu]

Dear Anupriya,
I would first do a full optimization (vc-relax) in other code (VASP/QE) for
such a large system and then using this fully optimized structure, I will
do an ion relaxation (run_lapw .... -min) in Wien2k.

If you want to do everything using Wien2k, please follow Prof. Peter's
response.

Happy computing

Regards
Bhamu

On Sat, Oct 23, 2021, 3:27 AM Peter Blaha <pblaha at theochem.tuwien.ac.at>
wrote:

> A full optimization of a bigger triclinic structure is hardly possible
> with WIEN2k.
>
> It depends a lot on what the purpose of your calculations is, but:
>
> a) Most importantly, optimize the position of the atoms using the
> forces:   run_lapw  -min ...
>
> b)  eventually I'd next do a volume optimization (x optimize, option 1)
> Do not forget the   -min switch in run_lapw, otherwise the results are
> nonsense. Volume changes give the largest change in E-tot.
> Note, that other separate options of x optimize are rather useless for
> this purpose. One cannot optimize alpha,beta,gamma for fixed a,b,c. This
> is nonsense.
>
> c) eventually you may use   optimize_abc_lapw -t 3 ...
> This optimizes a,b,c independently but simultaneously. Again don't
> forget the -min switch.
>
> For such a large cell, such calculations can be very time consuming when
> you do not use well adapted parameters (RKmax, k-points) and a good
> parallelization strategy on a sufficient number of cores.
>
> Am 22.10.2021 um 04:54 schrieb Anupriya Nyayban:
> > Dear users and experts,
> >
> > I have a triclinic structure (P1 space group) with lattice parameters
> > a=18.508, b=39.835, c=40.199 Bohr; α = 119.701 ◦ , β = 103.309 ◦ , γ =
> > 90.0 ◦.  I have the following doubts
> > 1) The volume obtained with these lattice parameters as well angles
> > (with the formula for triclinic cell) is not the same as the volume
> > (24823.466 Bohr^3) found in the scf file (VOL).
> > 2) The mailing list suggests volume optimization by a) varying a, b, c
> > while α, β, γ are constant; b) varying α, β, γ with fixed a, b, c. I
> > have done volume optimization by varying volume with constant a:b:c. But
> > I am not able to find the suitable switch for the case b) in the
> > optimize.job script.
> > Your valuable suggestion is highly appreciated!!
> >
> > Thank you!!
> > --
> > With regards
> > Anupriya Nyayban
> > Ph.D. Scholar
> > Department of Physics
> > NIT Silchar
> >
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> >
>
> --
> --------------------------------------------------------------------------
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
> Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
> WWW:   http://www.imc.tuwien.ac.at
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