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 <degir...@sissa.it <mailto:degir...@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)






    _______________________________________________
    Pw_forum mailing list
    Pw_forum@pwscf.org <mailto:Pw_forum@pwscf.org>
    http://pwscf.org/mailman/listinfo/pw_forum
    <http://pwscf.org/mailman/listinfo/pw_forum>



    _______________________________________________
    Pw_forum mailing list
    Pw_forum@pwscf.org <mailto:Pw_forum@pwscf.org>
    http://pwscf.org/mailman/listinfo/pw_forum
    <http://pwscf.org/mailman/listinfo/pw_forum>




_______________________________________________
Pw_forum mailing list
Pw_forum@pwscf.org
http://pwscf.org/mailman/listinfo/pw_forum


_______________________________________________
Pw_forum mailing list
Pw_forum@pwscf.org
http://pwscf.org/mailman/listinfo/pw_forum

Reply via email to