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[<drhendry@gmail.com>]

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