ABINIT Discussion Forums

Dear All,

I calculated several spontaneous polarizations of perovskite type oxide (BaTiO3 or something) by changing tetragonality of crystal i.e., c/a.
Obtained results is convex upward curve at c/a=1.1 or so.
I did not understand this is correct or not.
Does anyone tell me that spontaneous polarization depends on c/a linearly, or never decease by inceasing c/a?

I referred "http://forum.abinit.org/viewtopic.php?f=8&t=67", and my input files is as follows.

=======================================================
# BaTiO3 : computation of the total energy

ndtset 3

##### dataset 01
#Definition of the atomic positions without relaxing the lattice parameters and fixed Pb
optcell1 0
ionmov1 2
kptopt1 3

natfix1 1
iatfix1 1

#Definition of the atoms
xred
0.000000000000 0.000000000000 0.000000000000
0.500000000000 0.500000000000 0.545165431027
0.500000000000 0.500000000000 -0.094679657655
0.000000000000 0.500000000000 0.436894626777
0.500000000000 0.000000000000 0.436894626777

tolmxf1 1.0d-6
toldff1 1.0d-7

##### dataset 02
#Definition of the basis of the geometry determined by dataset 1 (so using getxcart 1)
kptopt2 1
getxcart2 1

toldfe2 1.0d-6

tolmxf2 1.0d-6
#toldff2 1.0d-6

##### dataset 03
getxcart3 1
kptopt3 3
getwfk3 -1
berryopt3 -1
rfdir3 1 1 1
bdberry3 1 20

toldfe3 1.0d-6

#####################################
# COMMON INPUT DATA

#Definition of the unit cell
acell 3.9940 3.9940 4.59310 angstrom
rprim 1.0 0.0 0.0
0.0 1.0 0.0
0.0 0.0 1.0

#Definition of the atom types
natom 5
typat 1 2 3 3 3
ntypat 3
znucl 56 22 8


#Definition of the planewave basis set
ecut 45.0

# find the optimal total energy
ntime 30
nband 20

#Definition of the k-point grid
ngkpt 10 10 10
#nshiftk 1
#shiftk 0.5 0.5 0.5

#Definition of the SCF procedure
nstep 100
diemac 12.0


--
Minamoto, Satoshi