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[avanderg <avanderg@mines.edu>]

Hello All,

I am trying to find the equlibrium lattice constant for ferromagnetic 
FCC Ni.  Unfortunately I am running into several problems:

1)the latice constant of the conventional cell becomes far too large 
compared to experimental (abinit ->8.9367bohr ;experimental ->6.6598 bohr).

2) this should be a 1 degree of freedom problem (optcell = 1) but it 
takes about 13 hours to get the above result which seems like a long 
time to me (and I have done convergence tests on things like kpts and ecut).

3)if I use optcell = 2 (letting rprim be optimized as well as acell), 
the system becomes tetragonal even after inputting a fcc crystal. I 
wouldn't think anything would break the symmetry  and the system would 
stay fcc.

Thanks in advance for the help

Abram Van Der Geest


Input File:

#Crystalline Nickel: looking for Eq acell


kptopt   1
kptrlatt -17 17 0
             0 17 0
             0 17 -17
shiftk   0.0 0.0 0.0

toldfe   1.0d-6
getwfk   -1

nsppol   2               #Ni is magnetic
spinat  0.0 0.0 2.0  #breaking symmetry using Hund's rule

#options for optimizing lattice parameters
optcell 1
ionmov  3
ntime  25
dilatmx 1.6  #abinit says anything less is too small
ecutsm  0.5

#Input Variables for both
occopt    4
tsmear  0.04

nband  20

#Def of unit cell
acell     3*4.7092       #a of the primitive cell
rprim     0.0 0.5 0.5    #FCC prim vectors
         0.5 0.0 0.5
         0.5 0.5 0.0

#def of atom
ntypat    1              #1 type of atom
znucl     28             #and it is Ni

natom     1              #1 atom
typat     1              #what is the type of each atom

xred      0.0 0.0 0.0    #location of each atom
ixc       1              #LDA Teter Pade parametrization
ecut      55             #50 = medium ecut
diemac    1.0d6          #preconditions SCF
nstep     20