<div dir="ltr"><img width="0" height="0" class="mailtrack-img" alt="" style="display:flex" src="https://mailtrack.io/trace/mail/858544a2255f68a3a660de7a36104885ba220589.png?u=674019"><div>Dear WIEN2K users.</div><div><br></div><div>My project involves XPS study of adsorbed molecules on the surface of graphene.</div><div>As a starting point, I have tried to calculate binding energy for a 1S core state of pristine graphene but I did not succeed. The value 296.8 eV I have got is too far from the experimental results 284.5 eV.</div><div>Currently, I am using 16.1 version of WIEN2K.</div><div>In my calculations, I have used R*Kmax=7 and 6x6x1 k-points mesh, so it is should be a fairly good numbers. I have tried to increase another parameter Gmax from the 12 to 14 but the result is more or less the same.</div><div><br></div><div>Basically, from the WIEN2K forum and presentation slides, I understood that delta-SCF method should be quite precise. It claimed that by using WIEN2K it is possible to reproduce experimental values for TiC, Ti4C4 and TiN within error less than 1%.</div><div><br></div><div>The procedure I have followed in order to calculate core binding energy is following:</div><div>1)<span style="white-space:pre"> </span>Create large enough supercell in order to avoid hole-hole interaction.</div><div>2)<span style="white-space:pre"> </span>To do an SCF calculation for a ground state of that supercell where I can grab a total energy Eg for the ground state.</div><div>3)<span style="white-space:pre"> </span>Choose one single atom in the supercell to be perturbed (ionised) which correspond to the element of interest.</div><div>4) <span style="white-space:pre"> </span>Take away one electron from the core state you want to study in that atom by changing an occupation number in the case.inc. In the pristine graphene case, it is the 1S state in one of the supercell atoms. So for graphene, you have to change occupation of 1S orbital from the 2 to 1.</div><div>5)<span style="white-space:pre"> </span>Then in order to enforce charge neutrality of the supercell, you should put BG charge equal -1 in the case.inm file.</div><div>6)<span style="white-space:pre"> </span>Do an SCF calculation for an excited system which will give you a value of total energy for the ionised supercell - Eexc.</div><div><br></div><div>So, in principle, the difference Eb=Eg-Eexc should give me the XPS shift for the chosen core state. And if your supercell is big enough the results should be close to the experimental value.</div><div><br></div><div>Here are some results for few different parameters and supercells:</div><div>4x4 supercell R*Kmax=7 Gmax=14</div><div>k-points 4x4x1 dE=296.787287946 eV</div><div>k-points 6x6x1 dE=296.87888205 eV</div><div><br></div><div>3x3 supercell R*Kmax=7 Gmax=12</div><div>k-points 6x6x1 dE=298.147365363 eV</div><div>R*Kmax=6 k-points 3x3x1 dE=297.998728554</div><div>R*Kmax=5 k-points 3x3x1 dE=298.51212406</div><div><br></div><div>5x5 supercell R*Kmax=7 Gmax=12</div><div>k-points 4x4x1 dE=297.039874874</div><div><br></div><div>Talking about Slater transition method - it gives me an even worse number.</div><div>So, I took 3x3 super cell with a 1/2 core-hole.</div><div>The 1s level energy of perturbed C atom is -25.266283216 Ryd. Fermi energy is -0.5810770100 Ryd.</div><div>So Eb= -24.6852062060=335.859462333 eV - very bad.</div><div><br></div><div>Am I doing something wrong or misunderstanding something?</div><div>Could it be a problem with WIEN2K compilation? </div><div>I have tried to calculate DOS and charge density for a pristine graphene and they look reasonable.</div><div><br></div><div><div class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div><font color="#cccccc" face="georgia, serif">==============================================</font></div><div dir="ltr"><div dir="ltr"><b style="color:rgb(34,34,34);font-weight:bold"><font color="#6fa8dc" size="2" face="monospace, monospace">With best regards, </font></b><div style="color:rgb(34,34,34);font-weight:bold"><b><font color="#6fa8dc" size="2" face="monospace, monospace"> Kartsev Alexey.</font></b></div><div style="font-weight:bold"><span style="background-color:rgb(255,255,255)"><font color="#ea9999" size="2" face="monospace, monospace"><br></font></span></div><div><font color="#3d85c6" size="2" face="monospace, monospace">Postdoc Fellow<span style="background-color:rgb(255,255,255)"> </span></font></div><div><div><div><font color="#3d85c6" size="2" face="monospace, monospace">Atomistic Simulation Centre,</font></div><div><font color="#3d85c6" size="2" face="monospace, monospace">School of Mathematics and Physics,</font></div><div><font color="#3d85c6" size="2" face="monospace, monospace">Queen's University Belfast,</font></div><div><font size="2" face="monospace, monospace"><font color="#3d85c6">Belfast BT7 1NN, </font><span style="color:rgb(61,133,198)">Northern Ireland,</span></font></div><div><font color="#3d85c6" size="2" face="monospace, monospace">United Kingdom</font></div></div></div><font color="#674ea7" size="2" face="monospace, monospace">E-mail: </font><font color="#0000ee" face="monospace, monospace" size="2"><u><a href="mailto:A.Kartsev@qub.ac.uk">A.Kartsev@qub.ac.uk</a></u></font><div><font size="2" face="monospace, monospace"><img src="https://uk.campusclothing.com/Uploads/University/Images/30.jpg" width="200" height="75" style="color: rgb(224, 102, 102);"><br></font></div><div style="color:rgb(34,34,34);font-weight:bold"><font size="2" face="monospace, monospace"><br></font></div><div><br></div></div></div><div><br></div></div></div></div></div></div></div></div></div></div></div></div></div></div>
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