<div dir="ltr">Dear Vivek,<div>0) I recommend you to read instructions for "mstar" which gives more explanations than UG of optic. <br><div>1) If your system does not have an inversion center (I suspect that TaAs does not), the calculation of velocity with spin-orbit needs an additional step in mimicking the spin-polarized calculations [1]. </div><div>This is explained in UG, check paragraph 8.20.1 </div><div>2) To have all matrix elements calculated, ask optic to compute all 9: line 3 of case.inop should be 9, and lines 4-12: 1 2 3 4 5 6 7 8 9 respectively.</div><div>3) The results are in file case.mommat2 or case.mommat2up file.</div><div>4) As for your question about half of matrix elements calculated, the others are complex conjugated. </div><div><br></div><div>Sincerely yours,</div><div>Mikhail Nestoklon</div><div><br></div><div>[1] $ cp case.vsp case.vspup</div> $ cp case.vsp case.vspdn<br> $ cp case.vectorso case.vectorsoup<br> $ cp case.energyso case.energysoup<br> $ x lapw2 -fermi -so -up<br> $ x optic -so -up</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sat, 25 May 2024 at 23:29, VIVEK PANDEY <<a href="mailto:vivek6422763@gmail.com">vivek6422763@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">Dear Wien2K community,<div> I am currently using the latest version of the WIEN2k package (<b>Version: WIEN2k_23.2</b>). At certain point of my work, I am in need of velocity term ( <b><<i>nk</i>|vx|<i>mk</i>></b> ), where <i>nk</i> and <i>m</i>k are the indices of Bloch states. Here, <i><b>n</b></i> & <i><b>m</b></i> denotes the band-indices and <i><b>k</b></i> stands for the particular <i><b>k</b></i>-point of the Brillouin zone. I found from here (<a href="https://triqs.github.io/dft_tools/latest/faqs/faqs.html#x-optic-does-not-write-a-case-pmat-file" target="_blank">https://triqs.github.io/dft_tools/latest/faqs/faqs.html#x-optic-does-not-write-a-case-pmat-file</a>) that one can obtain the velocity term using the <b><i>x optic</i></b> module. For this, I need to modify the <b><i>case.inop</i></b> file as mentioned in the above link. The velocity term will be contained in the <b><i>case.pmat</i></b> file.</div><div><br></div><div>I have performed the calculations on TaAs. My <i style="font-weight:bold">TaAs.inop </i>file look-like:</div><div><br></div><div>100 1 number of k-points, first k-point<br>-0.2 0.2 9999 Emin, Emax for matrix elements, NBvalMAX<br>2 number of choices (columns in *outmat): 2: hex or tetrag. case<br>1 Re xx<br>3 Re zz<br>ON ON/OFF writes MME to unit 4<br>1<br></div><div><br></div><div>So, as mentioned in the <i style="font-weight:bold">TaAs.inop </i>file, I want to calculate the velocity term for 100 <b><i>k</i></b>-points. These <b><i>k</i></b>-points are already contained in my <b><i>TaAs.klist</i></b> file.</div><div><br></div><div>After running the command: <b><i>x optic -so</i></b>, the obtained <b><i>TaAs.pmat</i></b> file look-like (I am providing the data of initial 2 <b><i>k</i></b>-points):</div><div><br></div><div> 1 67 68<br> 0.000000000000 0.000000000000 0.000000000000 1<br> (-1.617771001625472E-004,1.226564556964964E-008)<br> (-1.439040550334954E-004,-1.379984625073599E-008)<br> (3.785649513346538E-011,-1.299045946281420E-005)<br> (-3.656362974619897E-003,4.416165542701399E-003)<br> (4.419121064225817E-003,3.653538690785011E-003)<br> (2.453482640439684E-007,-8.805238041136547E-009)<br> (1.617766828253836E-004,-1.226567120783516E-008)<br> (1.439043262718125E-004,1.378900067924048E-008)<br> (7.662998780467998E-012,8.582197920130107E-009)<br> 2 67 68<br> 0.100000000000 0.100000000000 0.000000000000 2<br> (1.395573059329797E-002,3.799018979369327E-007)<br> (1.395573021772884E-002,-3.799076130893441E-007)<br> (5.130244989109358E-010,-5.404839562596613E-006)<br> (1.657834175714330E-002,3.964486338191684E-003)<br> (1.657834294376005E-002,-3.964481019261168E-003)<br> (-2.893793368690930E-010,1.776652555720962E-003)<br> (1.918588062557931E-002,-2.109479429269941E-007)<br> (1.918588071334665E-002,2.109422247967537E-007)<br> (-5.090469730277025E-010,-5.689825446102657E-006)<br></div><div><br></div><div>I can see that at both these <b><i>k</i></b>-points, there falls two bands (indices: 67 & 68) within the energy window considered in the <b><i>TaAs.inop</i></b> file.</div><div><br></div><div>To understand the data in the <b><i>TaAs.pmat</i></b> file, I analysed another file that was produced, namely <i style="font-weight:bold">TaAs.symmat. </i>The data for the first two <b><i>k</i></b>-point in this file look-like:</div><div><br></div><div>SO 2 Re <x><x> Re <z><z> ALL<br><br> KP: 1 NEMIN NEMAX : 67 68 dE: -0.2 0.2 K: 1<br><br> 67 67 0.123929E-18 0.168529E-09<br> 67 68 0.000000E+00 0.000000E+00<br> 68 68 0.123929E-18 0.168529E-09<br><br> KP: 2 NEMIN NEMAX : 67 68 dE: -0.2 0.2 K: 2<br><br> 67 67 0.109837E-02 0.123092E-09<br> 67 68 0.000000E+00 0.000000E+00<br> 68 68 0.109837E-02 0.123092E-09<br></div><div><br></div><div>It is seen from the <i style="font-weight:bold">TaAs.symmat </i>file that at each <b><i>k</i></b>-point, there are data for three pairs of bands (67-67, 67-68 & 68-68). If the <i style="font-weight:bold">TaAs.pmat </i>file corresponds to these combinations of bands, then at each <b><i>k</i></b>-point, there should be 9 lines. This is because, corresponding to each pair of bands, there will be three components of velocity (vx, vy & vz). The results obtained in <b><i>TaAs.pmat</i></b> file seems to be consistent with this.</div><div><br></div><div>Here, I want to ask my question. In the <b><i>TaAs.pmat</i></b> file, I am getting the data for <b><<i>67 k</i>|vx|68 <i>k</i>> </b>but not the data for <b><<i>68 k</i>|vx|67 <i>k</i>>. Why? Will they both be same or anyway related to each other?</b></div><div><b><br></b></div><div>After<b> </b>going through the WIEN2k userguide, I found a line mentioning: "<i>The program <b>optic</b> generates the symmetrized squared momentum matrix elements</i>". Does it mean that for the above given case, the code is making a 2x2 velocity matrix (for the two band-indices 67 & 68 ) and then it is symmetrizing the matrix by following the formula (A+A_Transpose)/2 ? If this is the case, then the inter-band (<i>n</i> not equal to <i>m</i>) velocity will not be correct in the <b><i>TaAs.pmat</i></b> file. How can I obtain the correct value of the inter-band velocity?</div><div><br></div><div>Kindly help me with this. Also, please correct me if I am misinterpreting something at some point.</div><div><br></div><b>Thanks and Regards</b><br><br><b>Yours Sincerely</b><font color="#888888"><br>Vivek Pandey<br>Research Scholar<br>Indian Institute of Technology, Mandi<br></font><div><span style="color:rgb(136,136,136)">Himachal Pradesh, India</span> </div><div><br></div></div>
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