Hard to say anything about the qtl-b, since I do not know your
structure, your sphere sizes, your rkmax and for which atom/l the
problems occur.
It is not uncommon that c/a changes drastically with volume, since you
could have "soft" and "hard" axis, so that whith pressure one axes
changes much more than another. If you do not find a minimum (but have a
smooth curve), you need to extend the c/a search.
In all our recent posts (userguide, workshops, ...) it is highly
recommended to use run_lapw -min instead of the old min_lapw script
when optimizing internal positions.
In many cases this is much more efficient and stable, although the
"automatic stopping" of run_lapw -min is still sometimes problematic and
it takes too long to stop (minimizes positions to forces of 0.5 or below
gaining only very little energy, although one does request only an
accuracy of 2 mRy).
On 03/03/2017 03:38 AM, GOUTAM KUMAR GUPTA wrote:
Dear all
Kindly give your feedback on optimization. I am facing a lot of problem
of QTLB-error. also as suggested change energy parameter value to take
care of this error. but the problem is if we change energy parameter
then comparison of final energy in the scf with different volume or c/a
ratio become difficult.
kindly suggest any reference on optimization of tetragonal structures
for both volume and c/a ratio with relaxed atomic positions.
Thanks
On Fri, Feb 24, 2017 at 11:04 AM, GOUTAM KUMAR GUPTA
<pg201381...@iitj.ac.in <mailto:pg201381...@iitj.ac.in>> wrote:
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*
--
*Goutam Kumar Gupta*
*Mob:8561995547*
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