ABINIT Discussion Forums

Hi All,

I'm trying to optimize cell parameter of EuTiO3. However, I faced with strange Abinit system behaviour.
I started from experimental value of cubic cell parameter a=3.9050 A=7.3818 Bohr. The system was asked to perform an optimization using next input parameters:
------------------------------------cut-here------------------------------------
optcell 1
ionmov 3
ntime 10
dilatmx 3.05
ecutsm 0.5

#perovskite structure
natom 3
typat 1 2 3
xred
0 0 0
0.5 0.5 0.5
0.5 0.5 0.0

ixc 1
ecut 10

nstep 55
iscf 5
tolvrs 1.0d-5
------------------------------------cut-here------------------------------------

It took more than one day to calculate 5 steps out of 10. Originally, I set dilatmx parameter to be 1.05 but it lead to an error stating that I need to encrease the parameter.

Also I found that total energy decreases even after acell is 5% greater than experimental value (just compared two datasets with experimental 'a' and new expanded on 5% 'a'). It looks too strange... It might be a case I missed something as I'm a bit new to Abinit.

I use pseudopotentials from tutorial folder of the system.

Any suggestions/ideas? Thanks in advance!