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<p class="MsoNormal">Dear all!<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I am currently trying to simulate the electronic properties of CsPbBr3 in its low-temperature phase (orthorhombic; a=8.244, b=11.735, c=8.198 angstrom, according to Stoumpos; Cryst. Growth Des. 2013); My principle plan is to follow Radi
et al. (arXiv:1405.1706v2), who have done this using Wien2k, muffin-tin potentials. Eventually I want to continue processing this with YAMBO (doesn¡¯t take US PP), so I am using normcons PBE (from the standard repository).<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">However, the band-gap obtained is really tiny (without SOC, SOC is known to further reduce the gap in this material); I have done the following:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoListParagraph" style="text-indent:-18.0pt;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="mso-list:Ignore">1)<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>Used the CIF file provided by stoumpos et al to create my unit cell and double checked with xcrysden –pwi if it turns out properly<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-18.0pt;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="mso-list:Ignore">2)<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>Tested convergence wrt. Total energy leading to a good compromise with ecutwfc =60.0 (tested between 30 and 180 Ry) and a unshifted automatic 4x3x4 k-grid (tested up to 16x16x16).
<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-18.0pt;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="mso-list:Ignore">3)<span style="font:7.0pt "Times New Roman"">
</span></span><![endif]>Run Relax (gamma only) – scf – bands along G-X-S-R-G<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The resulting band structure is in the pdf. The band gap at R is so tiny (0.x eV) that I am not sure if applying scissors in yambo is justified. I also tried smaller degauss and fixed occupations to not much success. If someone can spot
an obvious error in my input or has any hint how I can improve my results I would be very grateful! Thank you in advance for your time and help!<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Yours,<o:p></o:p></p>
<p class="MsoNormal">Chris<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">PS: I have also tried a VC-relax which clearly favors a shrinking cell (the cubic phase of CsPbBr3 for example is a=5.605 A, so the Pnma cell is probably far away from 0K – how to deal with this problem when trying to do a 300K phase¡¦?)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">My scf input:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">&control<o:p></o:p></p>
<p class="MsoNormal"> calculation = 'scf'<o:p></o:p></p>
<p class="MsoNormal"> restart_mode='from_scratch',<o:p></o:p></p>
<p class="MsoNormal"> prefix='cspbbr3',<o:p></o:p></p>
<p class="MsoNormal"> pseudo_dir = '. /pseudo/',<o:p></o:p></p>
<p class="MsoNormal"> outdir='./'<o:p></o:p></p>
<p class="MsoNormal"> wf_collect=.true.<o:p></o:p></p>
<p class="MsoNormal"> verbosity='high'<o:p></o:p></p>
<p class="MsoNormal">/<o:p></o:p></p>
<p class="MsoNormal">&SYSTEM<o:p></o:p></p>
<p class="MsoNormal"> ibrav = 8<o:p></o:p></p>
<p class="MsoNormal"> celldm(1)= 15.5789<o:p></o:p></p>
<p class="MsoNormal"> celldm(2)= 1.4235<o:p></o:p></p>
<p class="MsoNormal"> celldm(3)= 0.9944<o:p></o:p></p>
<p class="MsoNormal"> nat = 5<o:p></o:p></p>
<p class="MsoNormal"> ntyp = 3<o:p></o:p></p>
<p class="MsoNormal"> ecutwfc =60.0<o:p></o:p></p>
<p class="MsoNormal"> occupations='smearing'<o:p></o:p></p>
<p class="MsoNormal"> smearing='mp'<o:p></o:p></p>
<p class="MsoNormal"> degauss=0.002<o:p></o:p></p>
<p class="MsoNormal"> force_symmorphic=.true.<o:p></o:p></p>
<p class="MsoNormal"> vdw_corr='grimme-d2'<o:p></o:p></p>
<p class="MsoNormal">/<o:p></o:p></p>
<p class="MsoNormal">&electrons<o:p></o:p></p>
<p class="MsoNormal">diago_full_acc=.true.,<o:p></o:p></p>
<p class="MsoNormal">conv_thr=1.0d-8<o:p></o:p></p>
<p class="MsoNormal">diagonalization='david'<o:p></o:p></p>
<p class="MsoNormal">electron_maxstep=300<o:p></o:p></p>
<p class="MsoNormal">/<o:p></o:p></p>
<p class="MsoNormal">ATOMIC_SPECIES<o:p></o:p></p>
<p class="MsoNormal"> Pb 207.20000 Pb.pbe-d-hgh.UPF<o:p></o:p></p>
<p class="MsoNormal"> Cs 132.90500 Cs.pbe-sp-hgh.UPF<o:p></o:p></p>
<p class="MsoNormal"> Br 79.90400 Br.pbe-hgh.UPF<o:p></o:p></p>
<p class="MsoNormal">ATOMIC_POSITIONS (crystal)<o:p></o:p></p>
<p class="MsoNormal">Pb 0.500000000 0.495569542 0.500000000<o:p></o:p></p>
<p class="MsoNormal">Cs 0.000000000 -0.000054173 0.000000000<o:p></o:p></p>
<p class="MsoNormal">Br 0.000000000 0.496389920 0.500000000<o:p></o:p></p>
<p class="MsoNormal">Br 0.500000000 0.002099521 0.500000000<o:p></o:p></p>
<p class="MsoNormal">Br 0.500000000 0.496980388 0.000000000<o:p></o:p></p>
<p class="MsoNormal">K_POINTS {automatic}<o:p></o:p></p>
<p class="MsoNormal">4 3 4 0 0 0<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">My bands input<o:p></o:p></p>
<p class="MsoNormal">nbnd=200 ! include plenty of empty bands for yambo<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">And<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">K_POINTS {crystal_b}<o:p></o:p></p>
<p class="MsoNormal">5<o:p></o:p></p>
<p class="MsoNormal"> 0.0000000000 0.0000000000 0.0000000000 10 !G<o:p></o:p></p>
<p class="MsoNormal"> 0.5000000000 0.0000000000 0.0000000000 10 !X<o:p></o:p></p>
<p class="MsoNormal"> 0.5000000000 0.5000000000 0.0000000000 10 !S<o:p></o:p></p>
<p class="MsoNormal"> 0.5000000000 0.5000000000 0.5000000000 10 !R<o:p></o:p></p>
<p class="MsoNormal"> 0.0000000000 0.0000000000 0.0000000000 10 !G<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div style="mso-element:para-border-div;border:none;border-bottom:solid windowtext 1.0pt;padding:0cm 0cm 1.0pt 0cm">
<p class="MsoNormal" style="border:none;padding:0cm">Christoph Wolf<o:p></o:p></p>
<p class="MsoNormal" style="border:none;padding:0cm"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Department of Materials Science and Engineering, POSTECH<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">RIST #3, 3152, San 31 Hyoja-dong, Nam-gu, Pohang, Kyungbuk, 790-784, Republic of Korea<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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