[Pw_forum] TiO2 001 Slab Convergence

[William Joseph Ivan DeBenedetti]

Dear QE Users,

I am attempting to perform convergence tests on an 001 slab of TiO2 (anatase) (1x1 with 1 layer of TiO2 in the c direction). While I am not getting any errors when attempting a ‘relax’ calculation, I am finding the the slab never really reaches a global minimum. I have decreased my convergence threshold and implemented Gaussian smearing but am still not reaching convergence. I have a ~ 15 angstrom vacuum layer implemented in the CELL_PARAMETERS block. Can someone who has more experience with surface slabs assist? This will eventually be used with an adsorbate for further studies.

I am including my input file:

&CONTROL
 calculation = 'relax',
 restart_mode = 'from_scratch',
 prefix='ANA',
 pseudo_dir='/work/04703/wjid/Pseudo',
 tstress=.true.,
 tprnfor=.true.,
/
&SYSTEM
 ibrav=0,
 nat=12,
 ntyp=2,
 ecutwfc=60,
 ecutrho=500,
 occupations='smearing',
 smearing='gaussian',
 degauss=0.01
/
&ELECTRONS
 conv_thr = 1.0D-6,
 mixing_mode = 'local-TF',
 mixing_beta = 0.3d0,
 diagonalization = 'cg',
/
&IONS
 ion_dynamics='bfgs',
/
&CELL
 cell_dynamics = 'bfgs',
 press=0.1d0,
/
ATOMIC_SPECIES
 Ti 47.88d0 Ti_PBE.UPF
 O  16.00d0 O_PBE.UPF

CELL_PARAMETERS
7.18366994d0   0.0d0      0.0d0
0.0d0   7.18366994d0      0.0d0
0.0d0   0.0d0     41.94037d0

ATOMIC_POSITIONS crystal
Ti     0.40773000000000      0.40773000000000   0.14705900000000
Ti     0.59227000000000      0.59227000000000   0.61764700000000
Ti     0.40773000000000      0.59227000000000   0.38235300000000
Ti     0.59227000000000      0.40773000000000   0.85294100000000
O      0.40773000000000      0.40773000000000   0.33529400000000
O      0.59227000000000      0.59227000000000   0.80588200000000
O      0.40773000000000      0.59227000000000   0.57058800000000
O      0.59227000000000      0.40773000000000   0.10000000000000
O      0.59227000000000      0.40773000000000   0.66470600000000
O      0.40773000000000      0.59227000000000   0.19411800000000
O      0.59227000000000      0.59227000000000   0.42941200000000
O      0.40773000000000      0.40773000000000   0.90000000000000

K_POINTS automatic
  4 4 1 0 0 0




Thanks,

Will DeBenedetti
Doctoral Candidate
Cornell University

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