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

Hi,

1) Have you tested non default mixing: iscf=7 or 2 (with eventually
small diemix ?)
2) for some such systems we have witnessed that state degeneracy may
prevent convergence. This usually can be solved with electronic
temperature. Sometimes tsmear as low as 30 Kelvin is enough. Have you
tryed this ?
3)Note that it may have been useful to include the output from the 10
first iterations. because It may tell if the preonditioner works
correctly. Did it ?
3') You may try to tune the computation of the dielectric matrix with
dielam and diegap (eventually diecut too). If you do so I'm interested
in being informed of potential accuracy improvements you will get.
3") Since you have no real vacuum you may also want to use iprcel 6X
instead of 4X. If this really helps, please let me know.

4) (not related with previous remarks) Your cell looks small for just
one kpt. Is really converged enough ?

regards.

PMA

On 2/2/07, zmq.lyao@gmail.com <zmq.lyao@gmail.com> wrote:
> Dear Abinit users,
>      I encounter a problem when I do a defect calculation. When I perform a 
> structure optimization of a supercell with a vacancy, the SCF can't converge. 
> The force and energy always oscillate and don't decrease. Because of this, 
> the structure optimization can't continue. I have tried the iprcel and diemix 
> parameter, but it still don't work. Anybody has some suggestions to solve 
> this problem? Thanks in advance.
>
> Regard,
> Zeming
>
> The input files is as following :
> ----------------
> optcell 0
> ionmov  2
> ntime  100
> nstep  200        # Maximal number of SCF cycles
> dilatmx 1.05
> ecutsm  0.5
> toldff = 1.0D-4
> tolmxf = 1.0D-3
> prtgeo 1
> prtden 0
> prtwf 0
>
> iprcel 49
> diemix 0.7
> ecut 70
>
> #Definition of the unit cell
> acell 14.703085  14.703085  22.539888       # 2X2X2
> angdeg 90 90 120
> chkprim 0
> brvltt 0
> #Definition of the atom types
> ntypat 2
> znucl 57 8
> natom 39
> typat 8*1 7*2 8*1 16*2
> xangst
>  1.123   1.945   1.455
>  1.123   1.945   7.418
>  1.123   5.835   1.455
>  1.123   5.835   7.418
>  4.492  -0.000   1.455
>  4.492  -0.000   7.418
>  4.492   3.890   1.455
>  4.492   3.890   7.418
>  1.123   1.945   3.856
>  1.123   1.945   9.820
>  1.123   5.835   3.856
>  1.123   5.835   9.820
>  4.492  -0.000   9.820
>  4.492   3.890   3.856
>  4.492   3.890   9.820
>  2.246   0.000   4.509
>  2.246   0.000  10.473
>  2.246   3.890   4.509
>  2.246   3.890  10.473
>  5.615  -1.945   4.509
>  5.615  -1.945  10.473
>  5.615   1.945   4.509
>  5.615   1.945  10.473
>  2.246   0.000   2.107
>  2.246   0.000   8.071
>  2.246   3.890   2.107
>  2.246   3.890   8.071
>  5.615  -1.945   2.107
>  5.615  -1.945   8.071
>  5.615   1.945   2.107
>  5.615   1.945   8.071
>  0.000   0.000   0.000
>  0.000   0.000   5.964
>  0.000   3.890   0.000
>  0.000   3.890   5.964
>  3.369  -1.945   0.000
>  3.369  -1.945   5.964
>  3.369   1.945   0.000
>  3.369   1.945   5.964
>
>
> #Definition of the k-point grid
> kptopt 0
> kpt 0 0 0


--
Pierre-Matthieu Anglade