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["Anglade Pierre-Matthieu" <anglade@gmail.com>]

You might get better results by simply increasing you number of bands.
Something like  (number of electron)/2 + (number of ion) might be
reasonnable for low temperatures (tsmear) and non spin polarized
computations.

On 4/19/06, jmlv@imr.ac.cn <jmlv@imr.ac.cn> wrote:
> Dear everyone:
>    I tried to get the equilbrium structure of TiNi unit cell (B2-structure, 
> 2 atoms/unit cell). But I always got a ERROR notice.
>
>    First, I used the default of nband=1. the ERROR says:
>     scfcge: ERROR -
>   Potential-based CG line minimization not converged after 13 restarts.
>   Action: read the eventual warnings about lack of convergence.
>   Some might be relevant. Otherwise, raise nband.
>
>    Then I followed what the code told me, changing the nband to 4, the 
> usual value for metals. There is an ERROR again, saying:
>     chkneu: ERROR -
>   Initialization of occ, with occopt=   3
>   There are not enough bands to get charge balance right
>   Action: modify input file...
>   (check the pseudopotential charges, the variable charge,
>   and the declared number of bands, nband)
>
>    What am I gonna do? Is there something wrong with the setting of nband? 
> Any suggestion would be appreciated. Thanks in advance.
>
>    The GGA-FHI pseudopotentials were used. The input file goes:
>
> # Relaxation of TiNi B2 phase unit cell
>
> #Definition of the unit cell
> acell  3*5.67        # Lattice constants.
> rprim  1.0 0.0 0.0   #
>        0.0 1.0 0.0   #
>        0.0 0.0 1.0   #
>
> #Definition of the atom types
> ntypat 2          # Type of constituent atoms.
> znucl 22 28       # Atomic number of each atom.
>
> #Definition of the atoms
> natom 2           # There are two atoms.
> typat 1 2         # One is Ti atom and another is Ni atom.
> xred              # Location of the atoms
>    0.0  0.0  0.0  # Triplet giving the REDUCED coordinate of atom 1.
>    0.5  0.5  0.5  # Triplet giving the REDUCED coordinate of atom 2.
>
> #Definition of the planewave basis set
> ecut  15.0        # Maximal kinetic energy cut-off, in Hartree
>
> #Definition of the k-point grid
> kptopt 1          # Automatic generation of k points, taking
>                   # into account the symmetry
> ngkpt 6 6 6       # This is a 2x2x2 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     # In cartesian coordinates, this grid is simple cubic, and
>   0.5 0.0 0.0     # actually corresponds to the
>   0.0 0.5 0.0     # so-called 4x4x4 Monkhorst-Pack grid
>   0.0 0.0 0.5
>
> #Definition of optimization parameters
> optcell    1         # Full optimization of cell geometry.
> ecutsm     0.5       # Default is 0.0. When optcell/=0, it should be larger 
> than zero.
> strprecon  0.001     # Default is 1.0. But in this case, it is decreased.
> ionmov     2         # Use the Broyden algorithm.
> dilatmx    3.0       # Default is 1.0. Here it is increased to 1.1.
> ntime      30        # Max. number of Broyden "time steps".
> tolmxf     1.0E-5    # Stopping criterion for geometry optimization.
>
> occopt     3      #
> tsmear     0.04   #
> ixc        11     #
> nband      4      # Changed from 1(the default) to 4(usually for metals) 
> after ABINIT's notice.
>
> #Definition of the SCF procedure
> nstep      100    # Maximal number of SCF cycles
> toldfe     1.0E-6 #
> diemac     1.0E6  #
>
> #Output control
> prtwf    0        # Do not creat the HUGE wavefunction file. Default is 1.
>
>
>


--
Pierre-Matthieu Anglade