[Wien] abnormal behaviour in lattice parameters with applied pressure

[Dr. K. C. Bhamu]

Dear Prof. Peter and other Wien2k users

*The parent structure file for all below calculations was well-optimized
one and then I performed two calculations with applied pressure.

I am trying to do pressure calculation of a ternary compound. I applied
pressure from 0 to 14GPa in step of 2GPa. Without optimization, I see a
clear decrease in the lattice parameters.
Unoptimised lattice parameters with mentioned pressure (in GPa).
0P  19.246483
2P  19.094359
4P  18.959055
6P  18.836998
8P  18.726089
10P  18.624460
12P  18.530711
14P  18.443746


But when I optimize the lattice parameters the lattice parameters first
decrease up to 4P then increase up to 12P and then decrease for 14P.

0P 19.248
2P 19.2479
4P 19.245
6P 19.248
8P 19.2489
10P 19.2504
12P 19.251
14P 19.2507
So my queries are:

1. Please comment on this trend in lattice parameters.

2. In the case of 0P and 6P, the optimized lattice parameters are same
which will give the same case.struct file. Obviously, the results for 0P
and 6P would be same. I wonder if someone could give input on this
situation. The applied pressure should change the properties.



Regards

Bhamu
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