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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