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

Hi,

When there is a lot of degrees of freedom the "ionmov 2" algorithm
looses some of its efficiency. It is not impossible that you get
better result with a viscous dumping or beeler molecular dynamics.

regards

PMA

On Wed, Mar 4, 2009 at 11:57 PM,  <drhendry@gmail.com> wrote:
> Hello,
>
> I'm trying to optimise the geometry of a 20 atom CaTiO3 orthorhombic bulk
> dielectric.  The process is taking considerably longer and does not seem to 
> be
> converging compared with a 6 atom TiO2 rutile bulk dielectric.  The max 
> force
> does not seem to go below ~ 1e-3, wheres TiO2 max force goes to machine
> precision.  I'm using Troullier-Martins psps and the input file is below.
>
> Could there be some way of improving this result, or is this to be expected?
>
> Thank you very much, in advance,
>
> David.
>
> #Definition of lattice parameters
> #********************************
>   acell  1.1034564219E+01  1.5140354875E+01  1.0791197046E+01
>
> #Definition of atomic positions and types
> #****************************************
>   natom       20
>   ntypat      3
>   znucl       20 22 8
>   typat       2 2 2 2 1 1 1 1 3 3 3 3 3 3 3 3 3 3 3 3
>   xcart
>  1.74102557844419E-21  6.94219419473125E-21  6.66433845029123E-21
>  5.51728210951351E+00  2.01064184754249E-07  5.39559852296522E+00
>  2.72273479496933E-07  7.57017743773540E+00  6.66433845029123E-21
>  5.51728238178699E+00  7.57017763879958E+00  5.39559852296522E+00
>  5.52568087138869E+00  3.78516729878331E+00  1.46347634448159E-02
>  -8.39821732821760E-03  1.13551877777517E+01  5.41023328641004E+00
>  -5.52568032684173E+00  1.13551875766875E+01 -1.46347634448159E-02
>  1.10429629809022E+01  3.78516749984750E+00  5.38096375952040E+00
>  -7.62652580040250E-03  3.78509505890158E+00 -2.23307892067039E-01
>  5.52490917986087E+00  1.13552600176334E+01  5.17229063089818E+00
>  7.62707034736165E-03  1.13552598165692E+01  2.23307892067039E-01
>  5.50965558371311E+00  3.78509525996576E+00  5.61890641503226E+00
>  2.78700708595054E+00  1.43408602047991E-01  2.66783642053104E+00
>  2.73027502356297E+00 -1.43408400983806E-01  8.06343494349627E+00
>  -2.78700845918014E+00  7.71358803235092E+00 -2.66784679121249E+00
>  8.30429111324061E+00  7.42676704418406E+00  2.72775173175273E+00
>  -2.78700708595053E+00 -1.43408602047991E-01 -2.66783642053104E+00
>  8.30428919546405E+00  1.43408803112175E-01  2.72776210243418E+00
>  2.78700900372710E+00  7.42676684311987E+00  2.66784679121249E+00
>  2.73027365033337E+00  7.71358823341510E+00  8.06344531417771E+00
>
> #Echange-correlation functional
> #******************************
>   #ixc         1
>
> #Plane wave basis and k-point grid
> #*********************************
>   ecut        30
>   ngkpt       7 5 7
>   nshiftk     1
>   shiftk      0.5 0.5 0.5
>   nband       48
>
> #Relax ions and unit cell
> #************************
>    #chkprim    0
>    #tsmear     0.01
>    kptopt     2
>    iscf       7
>    npulayit   7
>    iprcel     45
>    tolrff     0.02
>    #tolvrs     1.0d-18
>    #tolmxf     1.0d-8
>    nstep      200
>    optcell    2
>    ionmov     2
>    ntime      200
>    dilatmx    1.1
>    ecutsm     0.5
>    prtwf      0
>    prtden     0
>



-- 
Pierre-Matthieu Anglade