[Pw_forum] vc -relax converge

[Stefano de Gironcoli]

I think that usually it is convenient to relax the internal coordinates 
before staring moving the cell. did you tried that?
have you tried to use the bfgs algorithm in vc-relax ?
Stefano de Gironcoli - SISSA and DEMOCRITOS

ali kazempoor wrote:
> Dear all
> I use vc -relax to obtain the optimized lattice constant(tetragonal cell) and  also the atomic position around  O vacancy in TiO2 (2*2*3 supercell),but after 2 weeks , the pressure slowly goes from -100 kbar to -56 kbar( two far from 0.00. The input file is at following:
>  &control
>     calculation = 'vc-relax'
>     restart_mode='restart',
>     prefix='rutile-71atom'
>     tstress = .true.
>     tprnfor = .true.
>     pseudo_dir = './',
>     outdir='/ptmp/javad/scratch/'
> 	nstep=1000,
> 	dt=70,
>  /
>  &system
>     ibrav=  6 , celldm(1) =17.36,celldm(3)=0.9663585,  nat= 71, ntyp= 2,
>     ecutwfc =35.0,ecutrho=400
>  /
>  &electrons
>     diagonalization=''
>     mixing_mode = 'plain'
>     mixing_beta = 0.7
>     conv_thr =  1.0d-6
> /
>  &IONS
>  /
>  &CELL
> cell_dynamics = 'damp-w',
> press=00.0	
>  /
> ATOMIC_SPECIES
> Ti   43.0   Ti.pz-sp-van.UPF
> O    16.0   O.pz-van_ak.UPF
> ATOMIC_POSITIONS crystal
> Ti 0.00000000 0.00000000 0.00000000
> Ti 0.50000000 0.00000000 0.00000000
> Ti 0.00000000 0.50000000 0.00000000
> Ti 0.50000000 0.50000000 0.00000000
> Ti 0.00000000 0.00000000 0.33333333
> Ti 0.50000000 0.00000000 0.33333333
> Ti 0.00000000 0.50000000 0.33333333
> Ti 0.50000000 0.50000000 0.33333333
> Ti 0.00000000 0.00000000 0.66666667
> Ti 0.50000000 0.00000000 0.66666667
> Ti 0.00000000 0.50000000 0.66666667
> Ti 0.50000000 0.50000000 0.66666667
> Ti 0.25000000 0.25000000 0.16666667
> Ti 0.75000000 0.25000000 0.16666667
> Ti 0.25000000 0.75000000 0.16666667
> Ti 0.75000000 0.75000000 0.16666667
> Ti 0.25000000 0.25000000 0.50000000
> Ti 0.75000000 0.25000000 0.50000000
> Ti 0.25000000 0.75000000 0.50000000
> Ti 0.75000000 0.75000000 0.50000000
> Ti 0.25000000 0.25000000 0.83333333
> Ti 0.75000000 0.25000000 0.83333333
> Ti 0.25000000 0.75000000 0.83333333
> Ti 0.75000000 0.75000000 0.83333333
> O  0.65265000 0.15265000 0.00000000
> O  0.15265000 0.65265000 0.00000000
> O  0.65265000 0.65265000 0.00000000
> O  0.15265000 0.15265000 0.33333333
> O  0.65265000 0.15265000 0.33333333
> O  0.15265000 0.65265000 0.33333333
> O  0.65265000 0.65265000 0.33333333
> O  0.15265000 0.15265000 0.66666667
> O  0.65265000 0.15265000 0.66666667
> O  0.15265000 0.65265000 0.66666667
> O  0.65265000 0.65265000 0.66666667
> O  0.34735000 0.34735000 0.00000000
> O  0.84735000 0.34735000 0.00000000
> O  0.34735000 0.84735000 0.00000000
> O  0.84735000 0.84735000 0.00000000
> O  0.34735000 0.34735000 0.33333333
> O  0.84735000 0.34735000 0.33333333
> O  0.34735000 0.84735000 0.33333333
> O  0.84735000 0.84735000 0.33333333
> O  0.34735000 0.34735000 0.66666667
> O  0.84735000 0.34735000 0.66666667
> O  0.34735000 0.84735000 0.66666667
> O  0.84735000 0.84735000 0.66666667
> O  0.40265000 0.09735000 0.16666667
> O  0.90265000 0.09735000 0.16666667
> O  0.40265000 0.59735000 0.16666667
> O  0.90265000 0.59735000 0.16666667
> O  0.40265000 0.09735000 0.50000000
> O  0.90265000 0.09735000 0.50000000
> O  0.40265000 0.59735000 0.50000000
> O  0.90265000 0.59735000 0.50000000
> O  0.40265000 0.09735000 0.83333333
> O  0.90265000 0.09735000 0.83333333
> O  0.40265000 0.59735000 0.83333333
> O  0.90265000 0.59735000 0.83333333
> O  0.09735000 0.40265000 0.16666667
> O  0.59735000 0.40265000 0.16666667
> O  0.09735000 0.90265000 0.16666667
> O  0.59735000 0.90265000 0.16666667
> O  0.09735000 0.40265000 0.50000000
> O  0.59735000 0.40265000 0.50000000
> O  0.09735000 0.90265000 0.50000000
> O  0.59735000 0.90265000 0.50000000
> O  0.09735000 0.40265000 0.83333333
> O  0.59735000 0.40265000 0.83333333
> O  0.09735000 0.90265000 0.83333333
> O  0.59735000 0.90265000 0.83333333
> K_POINTS automatic
>  4 4 4   0 0 0 
> Have you any comment to accelerate the convergence?
> Thanks A lt
>  Ali KAzempour,Isfahan University of Technology,Physics Dept 
>
>
>       
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>