The ABINIT Users Mailing List ( CLOSED )

[Tanaka Yoshikazu <ytanaka@postman.riken.jp>]

Dear Xavier,

Thank you very much for your kind reply.

I am studing on phonons in BaVS3, which has hexagonal structure (a=6.74, 
c=5.61
angstroms) at room temperature.  This is a metal at room temperature, and
insulator below 70 K with orthorhombic structure.
I took the crystal structure from "Acta Cryst. B25 781 (1969).

First, I tried to calculate the total energy with the following
input file.

The result shows unusual forces among atoms 3,4,5 and 8,9,10.
(S atoms have strong forces each other.)
Does this means that the real existing crystal 
in hexagonal structure is unstable? 

Once I tried 
> #Optimization of the lattice parameters
> optcell 2
> ionmov  3
> ntime  10
> dilatmx 1.1
> ecutsm  0.5
but, the calculation did not complete becasue dilatmx 1.1 is not enough.

With regards,
Yoshikazu

> cartesian forces (hartree/bohr) at end:
>    1      0.00000000000000     0.00000000000000     0.00000000000000
>    2      0.00000000000000     0.00000000000000     0.00000000000000
>    3      0.00000000000000     0.04802739569869     0.00000000000000
>    4     -0.04159294475268    -0.02401369784935     0.00000000000000
>    5      0.04159294475268    -0.02401369784935     0.00000000000000
>    6      0.00000000000000     0.00000000000000     0.00000000000000
>    7      0.00000000000000     0.00000000000000     0.00000000000000
>    8      0.00000000000000    -0.04802739569869     0.00000000000000
>    9      0.04159294475268     0.02401369784935     0.00000000000000
>   10     -0.04159294475268     0.02401369784935     0.00000000000000
> frms,max,avg= 2.1478504E-02 4.8027396E-02   0.000E+00  0.000E+00  0.000E+00 
> h/b

Input file----------------------------------------------------------------
# Crystalline BaVS3 : computation of the total energy
#
  occopt   4
  tsmear 0.05
#Specific to ground state calculation
  kptopt   1            # Automatic generation of k points, taking
                        # into account the symmetry
#  tolvrs   1.0d-18      # SCF stopping criterion
    iscf   5            # Self-consistent calculation, using algorithm 5

#######################################################################
#Common input variables

#Definition of the unit cell
acell 6.724 6.724 5.610 angstrom
angdeg 90 90 120
spgroup 194
#rprim  1.0  0.0  0.0   # In lessons 1 and 2, these primitive vectors 
#       0.0  1.0  0.0   # (to be scaled by acell) were 1 0 0  0 1 0  0 0 1 
#       0.0  0.0  1.0   # that is, the default.

#Definition of the atom types
ntypat 3               # There are two types of atom
znucl 56 23 16         # The keyword "znucl" refers to the atomic number of 
the 
                       # possible type(s) of atom. The pseudopotential(s) 
                       # mentioned in the "files" file must correspond
                       # to the type(s) of atom. Here, type 1 is the Aluminum,
                       # type 2 is the Arsenic.

#Definition of the atoms
natom 10                # There are two atoms
typat 1 2 3 3 3 1 2 3 3 3
xred                   # This keyword indicate that the location of the atoms
   2/3  1/3 1/4
   0.0  0.0  0.0
   0.1656 0.3312 0.25
   0.6688 0.8344 0.25
   0.1656 0.8344 0.25
   1/3  2/3 3/4
   0.0  0.0  1/2
   0.8344 0.6688 0.75
   0.3312 0.1656 0.75
   0.8344 0.1656 0.75

#Exchange-correlation functional
ixc 1             # LDA Teter Pade parametrization

#Definition of the planewave basis set
ecut    6.0           # Maximal kinetic energy cut-off, in Hartree

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

#Definition of the SCF procedure
nstep 35               # Maximal number of SCF cycles
toldfe 1.0d-6

With regards,
Yoshikazu
-- 
Tanaka Yoshikazu, SPring-8/RIKEN
Mikazuki, Sayo, Hyogo 679-5148,
Portable Phone +81-7915-8-0802-0-3347,
Fax            +81-7915-8-2923
email          ytanaka@postman.riken.jp