<div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Hi Stefano and <span style="font-size:12.8px;font-family:arial,sans-serif">Giuseppe,</span></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><span style="font-size:12.8px;font-family:arial,sans-serif"><br></span></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Thanks for your feedback.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">I just wanted to try 48 atom supercell initially and see how it goes (to save computation time as well). I will try 108 atom supercell definitely. </div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Is EXX-ACE implemented in QE 6.1v by default or do I have to compile it separately?. I will try to run it (if our busy HPC facility permits!).</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">If I am not using HSE , do I have to use LDA level theory for TiO2 with defects?.</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Thanks</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Manu</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">(University of Waterloo)</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Sun, Aug 6, 2017 at 6:08 PM, Giuseppe Mattioli <span dir="ltr"><<a href="mailto:giuseppe.mattioli@ism.cnr.it" target="_blank">giuseppe.mattioli@ism.cnr.it</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
On the top of Stefano's answer, I would add that in a 48 atom<br>
supercell the interaction between the relaxation sphere of an oxygen<br>
vacancy and its periodic images along the 100 or 010 directions is too<br>
strong and can lead to an improper description of the electronic<br>
properties of the defect that can not be considered as an "isolated<br>
defect" anymore. I suggest that you use at least a 3x3x1 108-atom<br>
supercell. With the new EXX-ACE implementation you may probably afford<br>
an HSE calculation, otherwise remember also that the small-polaron<br>
character of excess electrons in TiO2 such as those induced by the O<br>
vacancy is not at all well described at the GGA level of theory.<br>
HTH<br>
Giuseppe<br>
<br>
stefano de gironcoli <<a href="mailto:degironc@sissa.it">degironc@sissa.it</a>> ha scritto:<br>
<span class=""><br>
> yes<br>
> start from the perfect relaxed geometry (as obtained from vc-relax)<br>
> remove an atom and relax the internal structure.<br>
> at the end also perform a vc-relaxation (from the fixed-cell relaxed<br>
> geometry)<br>
> stefano<br>
><br>
> On 06/08/2017 17:33, Manu Hegde wrote:<br>
>> Hello Stephano,<br>
>> Thanks for your reply. Just to double check what you meant before<br>
>> starting the calculations, you mean take the equilibrium values<br>
>> from the vc-relax calculation (perfect cell, only co-ordinates)<br>
>> and do the 'relax' calculation with defect?.<br>
>> Manu<br>
>> (University of Waterloo).<br>
>><br>
>><br>
>> On Sun, Aug 6, 2017 at 11:15 AM, stefano de gironcoli<br>
</span><div><div class="h5">>> <<a href="mailto:degironc@sissa.it">degironc@sissa.it</a> <mailto:<a href="mailto:degironc@sissa.it">degironc@sissa.it</a>>> wrote:<br>
>><br>
>> does the energy (enthalpy) decreases as the vc-relaxation<br>
>> progresses ?<br>
>> The local structure around the defect may be quite different. It<br>
>> may just take long.<br>
>><br>
>> I would start by performing a fixed cell relaxation with the cell<br>
>> parameters fixed at the undefected equilibrium values. And only<br>
>> after that I would start the vc-relax calculation from the so<br>
>> relaxed configuration to evaluate the vacancy formation volume.<br>
>> The local arrangement around the defect should be already more or<br>
>> less ok (if the supercell is large enough).<br>
>><br>
>> HTH<br>
>> stefano<br>
>><br>
>><br>
>><br>
>> On 06/08/2017 16:40, Manu Hegde wrote:<br>
>>> Hello,<br>
>>><br>
>>> I am trying to optimize anatase TiO2 supercell with 48 atoms. The<br>
>>> supercell converges in 15 BFGS cycles for a perfect cell. But<br>
>>> when I introduce defect (by removing one of the oxygen atom), the<br>
>>> vc-relax is not t all converging. I am using the same parameters<br>
>>> in both the cases. Can anyone give some feedback on this.?. Here<br>
>>> is my input,<br>
>>><br>
>>><br>
>>> &control<br>
>>> calculation = 'vc-relax' ,<br>
>>> restart_mode = 'from_scratch' ,<br>
>>> outdir = '/work/mhegde/tmp_tiodef/',<br>
>>> pseudo_dir = '/home/mhegde/tio_project/def_<wbr>tio/',<br>
>>> prefix = 'tioan',<br>
>>> verbosity = 'high',<br>
>>><br>
>>> /<br>
>>> &system<br>
>>> ibrav = 0,<br>
>>> nat = 47,<br>
>>> ntyp = 2,<br>
>>> ecutwfc =40,<br>
>>> ecutrho=400,<br>
>>> occupations='smearing',<br>
>>> degauss=0.003<br>
>>><br>
>>> /<br>
>>> &electrons<br>
>>> conv_thr = 1.D-6,<br>
>>> mixing_beta=0.1<br>
>>> /<br>
>>> &ions<br>
>>> ion_dynamics='bfgs'<br>
>>><br>
>>> /<br>
>>> &cell<br>
>>> cell_dynamics='bfgs'<br>
>>><br>
>>> /<br>
>>> ATOMIC_SPECIES<br>
>>> Ti 47.867000 Ti.pw91-nsp-van.UPF<br>
>>> O 15.99900 O.pw91-van_ak.UPF<br>
>>><br>
>>> ATOMIC_POSITIONS angstrom<br>
>>> Ti 0.00000000 2.84182500 1.20970000<br>
>>> Ti 1.89455000 2.84182500 3.62910000<br>
>>> O 0.00000000 0.94727500 1.99939216<br>
>>> O 0.00000000 2.84182500 4.41879216<br>
>>> O 1.89455000 0.94727500 2.83940784<br>
>>> Ti -1.89455000 0.94727500 -3.62910000<br>
>>> Ti 0.00000000 0.94727500 -1.20970000<br>
>>> O -1.89455000 -0.94727500 -2.83940784<br>
>>> O -1.89455000 0.94727500 -0.42000784<br>
>>> O 0.00000000 -0.94727500 -1.99939216<br>
>>> O 0.00000000 0.94727500 -4.41879216<br>
>>> Ti 0.00000000 -0.94727500 1.20970000<br>
>>> Ti 1.89455000 -0.94727500 3.62910000<br>
>>> O 0.00000000 -2.84182500 1.99939216<br>
>>> O 0.00000000 -0.94727500 4.41879216<br>
>>> O 1.89455000 -2.84182500 2.83940784<br>
>>> O 1.89455000 -0.94727500 0.42000784<br>
>>> Ti -1.89455000 -2.84182500 -3.62910000<br>
>>> Ti 0.00000000 -2.84182500 -1.20970000<br>
>>> O -1.89455000 2.84182500 -2.83940784<br>
>>> O -1.89455000 -2.84182500 -0.42000784<br>
>>> O 0.00000000 2.84182500 -1.99939216<br>
>>> O 0.00000000 -2.84182500 -4.41879216<br>
>>> Ti -3.78910000 2.84182500 1.20970000<br>
>>> Ti -1.89455000 2.84182500 3.62910000<br>
>>> O -3.78910000 0.94727500 1.99939216<br>
>>> O -3.78910000 2.84182500 4.41879216<br>
>>> O -1.89455000 0.94727500 2.83940784<br>
>>> O -1.89455000 2.84182500 0.42000784<br>
>>> Ti 1.89455000 0.94727500 -3.62910000<br>
>>> Ti -3.78910000 0.94727500 -1.20970000<br>
>>> O 1.89455000 -0.94727500 -2.83940784<br>
>>> O 1.89455000 0.94727500 -0.42000784<br>
>>> O -3.78910000 -0.94727500 -1.99939216<br>
>>> O -3.78910000 0.94727500 -4.41879216<br>
>>> Ti -3.78910000 -0.94727500 1.20970000<br>
>>> Ti -1.89455000 -0.94727500 3.62910000<br>
>>> O -3.78910000 -2.84182500 1.99939216<br>
>>> O -3.78910000 -0.94727500 4.41879216<br>
>>> O -1.89455000 -2.84182500 2.83940784<br>
>>> O -1.89455000 -0.94727500 0.42000784<br>
>>> Ti 1.89455000 -2.84182500 -3.62910000<br>
>>> Ti -3.78910000 -2.84182500 -1.20970000<br>
>>> O 1.89455000 2.84182500 -2.83940784<br>
>>> O 1.89455000 -2.84182500 -0.42000784<br>
>>> O -3.78910000 2.84182500 -1.99939216<br>
>>> O -3.78910000 -2.84182500 -4.41879216<br>
>>><br>
>>> K_POINTS {automatic}<br>
>>><br>
>>> 2 2 2 0 0 0<br>
>>><br>
>>> CELL_PARAMETERS angstrom<br>
>>><br>
>>> 7.57820000 0.00000000 0.00000000<br>
>>> 0.00000000 7.57820000 0.00000000<br>
>>> 0.00000000 0.00000000 9.67760000<br>
>>><br>
>>> Thanks,<br>
>>> Manu<br>
>>> (University of Waterloo)<br>
>>><br>
>>><br>
>>><br>
>>><br>
>>><br>
>>><br>
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Giuseppe Mattioli<br>
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