[Pw_forum] vc-relax convergence
stefano de gironcoli
degironc at sissa.it
Sun Aug 6 17:38:50 CEST 2017
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
> <degironc at sissa.it <mailto:degironc at sissa.it>> 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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