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[taokun76@hotmail.com]

Dear abinit user,

When I did some calculations on the fcc Cu with the parameter "optcell=2",the 
lattice contant that I choosed was close to the experimental data(6.82 Bohr). 
The log file indicates to increase the parameter "dilatmx" to "1.2". When it 
was increased to "1.2", I found that the lattice constant changed greatly 
from 6.82 Bohr to about 4.87 Bohr!! However when the papemeter "optcell=1", 
the calculated lattice constant was coincided with the experimental value. 
Perhaps, there is something wrong with my input file. Any comment would be 
appreciated, thanks in advance!

Attached below is my input file:

#Definition of the planewave basis set
ecut  30.0

#Definition of the unit cell
acell   3*6.83135994
rprim   0.0   0.5  0.5
        0.5   0.0  0.5
        0.5   0.5  0.0

#Definition of occupation numbers
occopt  4
tsmear  0.03

#Definition of the k-point grid
kptopt  1
ngkpt   6 6 6
nshiftk 4
shiftk  0.5  0.5  0.5
        0.5  0.0  0.0
        0.0  0.5  0.0
        0.0  0.0  0.5

#Definition of the atom types
ntypat  1
znucl   29

#Definition of the atoms
natom  1
typat  1
xred  
       0  0  0
       
#The relaxation
optcell 1
ionmov 3
dilatmx 1.05
ecutsm 0.5
ntime  100

#Exchange-correlation functional
ixc  11

#Definition of the SCF procedure
nstep 100
toldfe 1.0d-6     

Kun Tao