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[Xavier Gonze <gonze@pcpm.ucl.ac.be>]

Dear Tanaka Yoshikazu,

At least two input variables have questionable values :
- ecut  6    is likely much too low (for Vanadium, I guess you need  
at least 25 - remember convergence studies are up to the user)
- toldfe 1.0d-6 is likely too large for converged forces, and the use  
of toldfe is not recommended for structural optimization.
 Use toldff or tolvrs instead, e.g. with a value  toldff 1.0d-6

May be there are other problems ...
Xavier

On 06 Feb 2006, at 04:40, Tanaka Yoshikazu wrote:

> 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