[Wien] Problem in optimization

[GOUTAM KUMAR GUPTA]

Dear all

I am trying to optimize tetragonal Cu2ZnSnS4 lattice structure (lattice
constant and c/a ratio both). What i did is

1) first i perform volume optimization at -4, -2,0,2,4 with simultaneous
optimization of lattice positions using

min -I -j "run_lapw -I -fc 1.0 -i 40 "

in optimize.job script

my volume optimization run fine and i get minima at 4 % change.

2) then for each volume i performed c/a ratio optimization at -4,-2,0,2,4
using same command

min -I -j "run_lapw -I -fc 1.0 -i 40 " in optimize.job file

 Now during my c/a ratio optimization i got minima for 0%, 2% and 4% volume
case. but for -4% and -2% volume change i do not get minima and the c/a
ratio optimization curve do not show single minima. hence i am facing
problem in finding optimized lattice parameters with optimized lattice
position. as i an unable to get lowest energy structure.

2) Some times i see that for 0, 2, 4% volume change optimization runs well
but for lower volume change say 1% or 3% it shows QTLB error (keeping all
other parameters same). I do not know the exact reason for this.


Kindly give your feedback. If i am doing any wrong in optimization script
the kindly suggest modified optimization script for both volume and c/a
ratio optimization.


Thanks
-- 
*Goutam Kumar Gupta*
*Mob:8561995547*
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