[Wien] a note on lattice parameter optimization

[Dr. K. C. Bhamu]

Hello,

Using experimental lattice parameters(a Ang), I optimized the structure
with two options.

1. Directly optimized the structure without min_lapw ... and the optimized
lattice parameters are in the vicinity of Exp a (~0.01 Ang accuracy) and
the calculated band gap (from mBJ2) is in agreement with reported value
~0.3 eV less.

2. First relaxed the structure and then optimized this relaxed structure
(without min_lapw ....). In this case the optimized lattice parameters are
reduced by ~0.05 Ang and the band gap vanished or largely reduced.


Why is the second way of doing band structure not working?

I tested it on many systems. In some case system became metal and in some
cases band gap largely reduced when  I used the fully relaxed structure for
optimization.


Thanks,


Bhamu
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