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<p class="MsoNormal"><span lang="EN-GB">Dear QE users,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I have been performing calculations on surface-modified TiO<sub>2
</sub>for some time now, as I took over a research project from a previous PhD student who quit his PhD. The project was already running for some time so I based my calculations on his input files as I started to learn how to use QE. Now I’m reading a lot of
stuff online about performing QE calculations and I start to notice that my input files might be wrong...<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I am performing calculations on a 3-layer anatase (101) slab with a 20 Å vacuum width above it and adsorbing different adsorbates onto the surface. I just found out that apparently when you are adsorbing molecules onto
a slab you should use a dipole correction (dipfield = .TRUE.), which I did not do... I also read that for slab calculations it is recommended to use the assume_isolated keyword to cut off the Coulomb interaction in the z-direction and that the dipfield and
assume_isolated keyword should not be used simultaneously.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I tried reading the papers on dipfield and the different assume_isolated options but I’m still pretty new to QE and periodic calculations so I found them hard to understand completely... Therefore, I would be most grateful
if somebody could elaborate on the following questions:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<ol style="margin-top:0cm" start="1" type="1">
<li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo1"><span lang="EN-GB">Is it correct that you should use either dipfield or assume_isolated and not both at the same time? If so, which one is the best one to use?<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo1"><span lang="EN-GB">I don’t quite understand why you have to do a dipole correction when adsorbing a molecule on the surface, is this just due to the fact that you induce a dipole upon
binding and the PBC enlarge this effect?<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo1"><span lang="EN-GB">If assume_isolated is the way to go, which option should I use? From what I understand, I cannot use Makov-payne as it is “ONLY FOR CUBIC SYSTEMS” and my cell is
monoclinic (a=b</span><span style="font-size:11.5pt;font-family:"Segoe UI",sans-serif;color:#232629;background:white">≠</span><span style="font-size:11.5pt;color:#232629;background:white">c, α=ß=90°</span><span style="font-size:11.5pt;font-family:"Segoe UI",sans-serif;color:#232629;background:white">≠</span><b><span style="font-size:10.5pt;font-family:"EB Garamond";color:#202122;background:white">γ)</span></b><span lang="EN-GB">,
esm is also not an option as it “Requires cell with a_3 lattice vector along z, normal to the xy plane, with the slab centered around z=0.” which is not the case for my system. So this leaves 2D and martyna-tuckerman as possible options, but I can’t seem to
find a straight answer which is best or what the differences are.<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0cm;mso-list:l0 level1 lfo1"><span lang="EN-GB">What about the calculations I have already performed? Are they useless without applying a dipole and/or coulomb correction?<o:p></o:p></span></li></ol>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Thanks in advance!<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Léon Luntadila Lufungula<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Master student<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">University of Antwerp<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
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