The ABINIT Users Mailing List ( CLOSED )

["Aldo Humberto Romero" <aromero@qro.cinvestav.mx>]

Dear Yang

your cutoff energy is way to low... 12Ry for a TM pseudo
is really low (even in Vasp, which are are soft pseudos,
the cutoff is higher)... you should check energy convergence
as function of cutoff and then look at acell.

By the way, I have not experience with Ge,
but you can also play with the number
of Kpoints after you energy convergence study.

regards

-aldo.

> Dear All,
>
> I optimized the lattice constant of Ge following the ABINIT tutorial. The
> value I got is about 5.52Angstrom, which is not in good agreement with the
> experimental value (5.66Angstrom), the gap about 2%. I did the similar
> calculation using VASP, and the error is within 0.5%, so I think the
> lattice constant of Ge I got by ABINIT is not nice, but I don?t know where
> I lost. Can any one there help me to correct my input files or give me
> some suggestions? The pseudopotential I use is Troullier-Martins LDA
> pseudopotential, and the input file is like following.
>
> _____________________________
>
> # optimize the lattice constat
>
> optcell 1
>
> ionmov  3
>
> ntime  10
>
> dilatmx 1.1
>
> ecutsm  0.5
>
> #Definition of the unit cell
>
> acell 3*10.699         # This is equivalent to   10.62 10.62 10.62
>
> rprim  0.0  0.5  0.5   # In lessons 1 and 2, these primitive vectors
>
>        0.5  0.0  0.5   # (to be scaled by acell) were 1 0 0  0 1 0  0 0 1
>
>        0.5  0.5  0.0   # that is, the default.
>
>
>
> #Definition of the atom types
>
> ntypat 1          # There is only one type of atom
>
> znucl 32         # 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, the only type is Ge.
>
> #Definition of the atoms
>
> natom 2           # There are two atoms
>
> typat 1 1         # They both are of type 1, that is, Ge
>
> xred              # This keyword indicate that the location of the atoms
>
>                   # will follow, one triplet of number for each atom
>
>    0.0  0.0  0.0  # Triplet giving the REDUCED coordinate of atom 1.
>
>    1/4  1/4  1/4  # Triplet giving the REDUCED coordinate of atom 2.
>
>                   # Note the use of fractions (remember the limited
>
>                   # interpreter capabilities of ABINIT)
>
> #Definition of the planewave basis set
>
> ecut 12.0 # Maximal kinetic energy cut-off, in Hartree
>
> #Definition of the k-point grid
>
> kptopt 1          # Option for the automatic generation of k points,
> taking
>
>                   # into account the symmetry
>
> ngkpt  6 6 6      # This is a 6x6x6 grid based on the primitive vectors
>
>
>
> nshiftk 4         # of the reciprocal space (that form a BCC lattice !),
>
>                   # repeated four times, with different shifts :
>
> 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 SCF procedure
>
> nstep 60         # Maximal number of SCF cycles
>
> toldfe 1.0d-6     # Will stop when, twice in a row, the difference
>
>                   # between two consecutive evaluations of total energy
>
>                   # differ by less than toldfe (in Hartree)
>
> diemac 12.0
>
> Thanks.
>
>
>
> Best regards,
>
> Yang Ming
>
>
>
> ******
>
> Computational Condensed Matter Physics
>
> Department of Physics
>
> National University of Singapore
>
> Singapore, 117542
>
> Tel: (65) 65164335 (office)
>
> Email: mingyang@nus.edu.sg
>


-- 
Dr. Aldo Humberto Romero
FULL PROFESSOR CINVESTAV - Unidad Queretaro
Libramiento Norponiente 2000
Real de Juriquilla, CP 76230, Qro, Queretaro
Mexico

Phone: + 52 442 441 4909
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Email: aromero@qro.cinvestav.mx
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