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<div class="moz-cite-prefix">does the energy (enthalpy) decreases as
the vc-relaxation progresses ? <br>
The local structure around the defect may be quite different. It
may just take long.<br>
<br>
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). <br>
<br>
HTH<br>
stefano<br>
<br>
<br>
On 06/08/2017 16:40, Manu Hegde wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CA+g44DvHx=4aeoHBei2q5i2O1-8p-v5NeEWB_0gp=_j=nGNNUw@mail.gmail.com">
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<div class="gmail_default">
<div class="gmail_default"><font face="arial, helvetica,
sans-serif">Hello,</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"><br>
</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif">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,</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"><br>
</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"><br>
</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif">&control</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> calculation = 'vc-relax' ,</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> restart_mode = 'from_scratch'
,</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> outdir =
'/work/mhegde/tmp_tiodef/',</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> pseudo_dir =
'/home/mhegde/tio_project/def_tio/',</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> prefix = 'tioan',</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> verbosity = 'high',</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"><br>
</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> /</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> &system</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> ibrav = 0,</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> nat = 47,</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> ntyp = 2,</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> ecutwfc =40,</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> ecutrho=400,</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> occupations='smearing',</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> degauss=0.003</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"><br>
</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> /</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> &electrons</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> conv_thr = 1.D-6,</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> mixing_beta=0.1</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif">/</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif">&ions</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> ion_dynamics='bfgs'</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"><br>
</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif">/</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif">&cell</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> cell_dynamics='bfgs'</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"><br>
</font></div>
<div class="gmail_default"><span
style="font-family:arial,helvetica,sans-serif">/</span><br>
</div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif">ATOMIC_SPECIES</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> Ti 47.867000 Ti.pw91-nsp-van.UPF</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"> O 15.99900 O.pw91-van_ak.UPF</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif"><br>
</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif">ATOMIC_POSITIONS angstrom</font></div>
<div class="gmail_default"><font face="arial, helvetica,
sans-serif">
<div class="gmail_default">Ti 0.00000000
2.84182500 1.20970000</div>
<div class="gmail_default">Ti 1.89455000
2.84182500 3.62910000</div>
<div class="gmail_default">O 0.00000000
0.94727500 1.99939216</div>
<div class="gmail_default">O 0.00000000
2.84182500 4.41879216</div>
<div class="gmail_default">O 1.89455000
0.94727500 2.83940784</div>
<div class="gmail_default">Ti -1.89455000
0.94727500 -3.62910000</div>
<div class="gmail_default">Ti 0.00000000
0.94727500 -1.20970000</div>
<div class="gmail_default">O -1.89455000
-0.94727500 -2.83940784</div>
<div class="gmail_default">O -1.89455000
0.94727500 -0.42000784</div>
<div class="gmail_default">O 0.00000000
-0.94727500 -1.99939216</div>
<div class="gmail_default">O 0.00000000
0.94727500 -4.41879216</div>
<div class="gmail_default">Ti 0.00000000
-0.94727500 1.20970000</div>
<div class="gmail_default">Ti 1.89455000
-0.94727500 3.62910000</div>
<div class="gmail_default">O 0.00000000
-2.84182500 1.99939216</div>
<div class="gmail_default">O 0.00000000
-0.94727500 4.41879216</div>
<div class="gmail_default">O 1.89455000
-2.84182500 2.83940784</div>
<div class="gmail_default">O 1.89455000
-0.94727500 0.42000784</div>
<div class="gmail_default">Ti -1.89455000
-2.84182500 -3.62910000</div>
<div class="gmail_default">Ti 0.00000000
-2.84182500 -1.20970000</div>
<div class="gmail_default">O -1.89455000
2.84182500 -2.83940784</div>
<div class="gmail_default">O -1.89455000
-2.84182500 -0.42000784</div>
<div class="gmail_default">O 0.00000000
2.84182500 -1.99939216</div>
<div class="gmail_default">O 0.00000000
-2.84182500 -4.41879216</div>
<div class="gmail_default">Ti -3.78910000
2.84182500 1.20970000</div>
<div class="gmail_default">Ti -1.89455000
2.84182500 3.62910000</div>
<div class="gmail_default">O -3.78910000
0.94727500 1.99939216</div>
<div class="gmail_default">O -3.78910000
2.84182500 4.41879216</div>
<div class="gmail_default">O -1.89455000
0.94727500 2.83940784</div>
<div class="gmail_default">O -1.89455000
2.84182500 0.42000784</div>
<div class="gmail_default">Ti 1.89455000
0.94727500 -3.62910000</div>
<div class="gmail_default">Ti -3.78910000
0.94727500 -1.20970000</div>
<div class="gmail_default">O 1.89455000
-0.94727500 -2.83940784</div>
<div class="gmail_default">O 1.89455000
0.94727500 -0.42000784</div>
<div class="gmail_default">O -3.78910000
-0.94727500 -1.99939216</div>
<div class="gmail_default">O -3.78910000
0.94727500 -4.41879216</div>
<div class="gmail_default">Ti -3.78910000
-0.94727500 1.20970000</div>
<div class="gmail_default">Ti -1.89455000
-0.94727500 3.62910000</div>
<div class="gmail_default">O -3.78910000
-2.84182500 1.99939216</div>
<div class="gmail_default">O -3.78910000
-0.94727500 4.41879216</div>
<div class="gmail_default">O -1.89455000
-2.84182500 2.83940784</div>
<div class="gmail_default">O -1.89455000
-0.94727500 0.42000784</div>
<div class="gmail_default">Ti 1.89455000
-2.84182500 -3.62910000</div>
<div class="gmail_default">Ti -3.78910000
-2.84182500 -1.20970000</div>
<div class="gmail_default">O 1.89455000
2.84182500 -2.83940784</div>
<div class="gmail_default">O 1.89455000
-2.84182500 -0.42000784</div>
<div class="gmail_default">O -3.78910000
2.84182500 -1.99939216</div>
<div class="gmail_default">O -3.78910000
-2.84182500 -4.41879216</div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">
<div class="gmail_default">K_POINTS {automatic}</div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default"> 2 2 2 0 0 0</div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">CELL_PARAMETERS angstrom</div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default"> 7.57820000 0.00000000
0.00000000</div>
<div class="gmail_default"> 0.00000000 7.57820000
0.00000000</div>
<div class="gmail_default"> 0.00000000 0.00000000
9.67760000</div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">Thanks,</div>
<div class="gmail_default">Manu</div>
<div class="gmail_default">(University of Waterloo)</div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default"><br>
</div>
</div>
<div><br>
</div>
</font></div>
<div style="font-family:arial,helvetica,sans-serif"><br>
</div>
</div>
</div>
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