yes
start from the perfect relaxed geometry (as obtained from vc-relax)
remove an atom and relax the internal structure.
at the end also perform a vc-relaxation (from the fixed-cell relaxed
geometry)
stefano
On 06/08/2017 17:33, Manu Hegde wrote:
Hello Stephano,
Thanks for your reply. Just to double check what you meant before
starting the calculations, you mean take the equilibrium values from
the vc-relax calculation (perfect cell, only co-ordinates) and do the
'relax' calculation with defect?.
Manu
(University of Waterloo).
On Sun, Aug 6, 2017 at 11:15 AM, stefano de gironcoli
<[email protected] <mailto:[email protected]>> wrote:
does the energy (enthalpy) decreases as the vc-relaxation
progresses ?
The local structure around the defect may be quite different. It
may just take long.
I would start by performing a fixed cell relaxation with the cell
parameters fixed at the undefected equilibrium values. And only
after that I would start the vc-relax calculation from the so
relaxed configuration to evaluate the vacancy formation volume.
The local arrangement around the defect should be already more or
less ok (if the supercell is large enough).
HTH
stefano
On 06/08/2017 16:40, Manu Hegde wrote:
Hello,
I am trying to optimize anatase TiO2 supercell with 48 atoms. The
supercell converges in 15 BFGS cycles for a perfect cell. But
when I introduce defect (by removing one of the oxygen atom), the
vc-relax is not t all converging. I am using the same parameters
in both the cases. Can anyone give some feedback on this.?. Here
is my input,
&control
calculation = 'vc-relax' ,
restart_mode = 'from_scratch' ,
outdir = '/work/mhegde/tmp_tiodef/',
pseudo_dir = '/home/mhegde/tio_project/def_tio/',
prefix = 'tioan',
verbosity = 'high',
/
&system
ibrav = 0,
nat = 47,
ntyp = 2,
ecutwfc =40,
ecutrho=400,
occupations='smearing',
degauss=0.003
/
&electrons
conv_thr = 1.D-6,
mixing_beta=0.1
/
&ions
ion_dynamics='bfgs'
/
&cell
cell_dynamics='bfgs'
/
ATOMIC_SPECIES
Ti 47.867000 Ti.pw91-nsp-van.UPF
O 15.99900 O.pw91-van_ak.UPF
ATOMIC_POSITIONS angstrom
Ti 0.00000000 2.84182500 1.20970000
Ti 1.89455000 2.84182500 3.62910000
O 0.00000000 0.94727500 1.99939216
O 0.00000000 2.84182500 4.41879216
O 1.89455000 0.94727500 2.83940784
Ti -1.89455000 0.94727500 -3.62910000
Ti 0.00000000 0.94727500 -1.20970000
O -1.89455000 -0.94727500 -2.83940784
O -1.89455000 0.94727500 -0.42000784
O 0.00000000 -0.94727500 -1.99939216
O 0.00000000 0.94727500 -4.41879216
Ti 0.00000000 -0.94727500 1.20970000
Ti 1.89455000 -0.94727500 3.62910000
O 0.00000000 -2.84182500 1.99939216
O 0.00000000 -0.94727500 4.41879216
O 1.89455000 -2.84182500 2.83940784
O 1.89455000 -0.94727500 0.42000784
Ti -1.89455000 -2.84182500 -3.62910000
Ti 0.00000000 -2.84182500 -1.20970000
O -1.89455000 2.84182500 -2.83940784
O -1.89455000 -2.84182500 -0.42000784
O 0.00000000 2.84182500 -1.99939216
O 0.00000000 -2.84182500 -4.41879216
Ti -3.78910000 2.84182500 1.20970000
Ti -1.89455000 2.84182500 3.62910000
O -3.78910000 0.94727500 1.99939216
O -3.78910000 2.84182500 4.41879216
O -1.89455000 0.94727500 2.83940784
O -1.89455000 2.84182500 0.42000784
Ti 1.89455000 0.94727500 -3.62910000
Ti -3.78910000 0.94727500 -1.20970000
O 1.89455000 -0.94727500 -2.83940784
O 1.89455000 0.94727500 -0.42000784
O -3.78910000 -0.94727500 -1.99939216
O -3.78910000 0.94727500 -4.41879216
Ti -3.78910000 -0.94727500 1.20970000
Ti -1.89455000 -0.94727500 3.62910000
O -3.78910000 -2.84182500 1.99939216
O -3.78910000 -0.94727500 4.41879216
O -1.89455000 -2.84182500 2.83940784
O -1.89455000 -0.94727500 0.42000784
Ti 1.89455000 -2.84182500 -3.62910000
Ti -3.78910000 -2.84182500 -1.20970000
O 1.89455000 2.84182500 -2.83940784
O 1.89455000 -2.84182500 -0.42000784
O -3.78910000 2.84182500 -1.99939216
O -3.78910000 -2.84182500 -4.41879216
K_POINTS {automatic}
2 2 2 0 0 0
CELL_PARAMETERS angstrom
7.57820000 0.00000000 0.00000000
0.00000000 7.57820000 0.00000000
0.00000000 0.00000000 9.67760000
Thanks,
Manu
(University of Waterloo)
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