[Pw_forum] vc-relax
Stefano de Gironcoli
degironc at sissa.it
Wed May 6 08:39:03 CEST 2009
have you tried to relax the internal coordinates before using vc-relax ?
there is a coupling between internal and cell degrees of freedom and
maybe what you see is just the effect of the internal degrees of freedom
(that are many in your case) slowly (because of the damp dynamics
algorithm) approaching their equilibrium values.
have you tried the bfgs algorithm in vc-relax ?
stefano de Gironcoli - SISSA and DEMOCRITOS
ali kazempoor wrote:
> Dear All
> I want to study an O vacancy in 2*2*3 supercell for TiO2. I use from vc-relax to optimize the lattice constant either with atomic relaxation. But from one week ago, the pressure evolved around 0.00 and dident go to zero .for example
> (kbar) P= 0.07
> (kbar) P= -0.45
> (kbar) P= -0.23
> (kbar) P= -0.25
> (kbar) P= -0.34
> (kbar) P= -0.40
> (kbar) P= -0.36
> (kbar) P= -0.14
> (kbar) P= -0.57
> (kbar) P= -0.41
> (kbar) P= -0.45
> (kbar) P= -0.83
> (kbar) P= -0.45
> (kbar) P= -0.37
> (kbar) P= -1.58
> (kbar) P= -1.00
> (kbar) P= -0.71
> (kbar) P= -0.73
> (kbar) P= -0.61
> (kbar) P= -0.58
> (kbar) P= -0.39
> (kbar) P= -0.89
> (kbar) P= -0.58
> (kbar) P= -0.33
> (kbar) P= -0.37
> (kbar) P= 0.59
> (kbar) P= -0.42
> (kbar) P= -0.61
> (kbar) P= -1.22
> (kbar) P= -1.68
> (kbar) P= -0.23
> (kbar) P= -0.20
> (kbar) P= -0.17
> (kbar) P= -0.39
> (kbar) P= -0.29
> (kbar) P= -0.76
> (kbar) P= -0.30
> (kbar) P= -0.24
> what can I do for this problem?
> Here is input file:
>
>
>
> &control
> calculation = 'vc-relax'
> restart_mode='restart',
> prefix='rutile-71atom'
> tstress = .true.
> tprnfor = .true.
> pseudo_dir = './',
> outdir='/ptmp/javad/scratch/'
> nstep=1000,
> dt=100,
> /
> &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-4
> /
> &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
> 3 3 2 1 1 1
> thanks alot
> Ali Kazempour,Isfahan University of Technology
>
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