<div dir="ltr">Dear Quantum-ESPRESSO,<div><br></div><div><br></div><div>I am trying to calculate phonon related property of 2-dimensional transition metal dichalcogenide(TMDC) and i have several questions about electron-phonon matrix calculation;</div><div><div><br></div><div><div>elphmat(j,i) = <psi_{k+q,j}|dvscf_q*psi_{k,i}><br></div><div><br></div><div>in code "elphon.f90"</div><div><br></div><div>From developer manual and source code of ph.x, I found that the electron-phonon matrix is written in the file "elph.#iq.#irr.xml" in q-point and irrep(irreducible representation) wise manner.</div><div><br></div><div>There are three questions.</div><div><br></div><div><br></div><div>1)<br></div><div><br></div><div>Since my unitcell(2-D TMDC monolayer slab with vacuum) has one metal atom and two surfur atoms, there are 9 normal modes in total.</div><div><br></div><div>At gamma point(q-point), there are only 6 irreps and thus 6 elph.1.#irr.xml files where #irr runs from 1 to 6 due to degeneracy, </div><div><br></div><div>However, where q-point!=0 without such degeneracy, there are 9 irreps and corresponding 9 elph.#iq.#irr.xml files.</div><div><br></div><div>So, i cannot figure out how i can get collection of xml files which correspond to the specific normal mode i concern for all q-points(by collecting xml files for q=0 and q!=0).</div><div><br></div><div>Numbering each mode or irrep even does not seem to follow magnitude of the phonon frequency. I also looked into relevant ph.x source codes but i couldn't understand.</div><div><br></div><div><br></div><div>2)</div><div><br></div><div>I want to know which physical quantity the values in elph.#iq.#irr.xml stand for.</div><div><br></div><div>The developer manual of ph.x reads;</div><div><div><br></div><div>"elph.#iq.#irr.xml contains the contribution to the electron phonon coefficients at the q vector #iq of the representation #irr. These files are written by elphel and contain the quantities g_qν (k, i, j) (see User Manual)."</div></div><div><br></div><div>and g_qν (k, i, j) seems to contain factor "sqrt[h/(2*M*w)]" followed by <psi_{k+q,j}|dvscf_q*psi_{k,i}></div><div><br></div><div>from User Manual.<br></div><div><br></div><div>But, i found that the values of g_qν (k, i, j) in elph.#iq.#irr.xml do not change with mass of atoms (To check this, i artificially change mass of surfur atoms to 100000)</div><div><br></div><div>I also, wondering the value in elph.#iq.#irr.xml are whether</div><div><br></div><div><\psi(k+q)|dV_{SCF}/du^q_{i a}|\psi(k)> (which is written in elphon.f90) <br></div><div><br></div><div>or just, </div><div><br></div><div><psi_{k+q,j}|dvscf_q*psi_{k,i}> <br></div><div><br></div><div><br></div><div>3)</div><div><br></div><div>It seems little trivial, I want to know some detail inside the elph.#iq.#irr.xml. </div><div><br></div><div>Following is my elph.1.1.xml</div><div><br></div><div>------elph.1.1.xml--------</div><div>...</div><div><br></div><div><div> <NUMBER_OF_BANDS type="integer" size="1"></div><div> 17</div><div> </NUMBER_OF_BANDS></div><div> <K_POINT.1></div><div> <COORDINATES_XK type="real" size="3" columns="3"></div><div> 0.000000000000000E+000 0.000000000000000E+000 0.000000000000000E+000</div><div> </COORDINATES_XK></div><div> <PARTIAL_ELPH type="complex" size="289"></div><div>-1.145849195795035E-003,-8.341398318595372E-013</div><div> 8.430451497377110E-012, 1.448582735931787E-011</div><div> 9.829111482844918E-009,-8.516622246844407E-010</div><div>-1.370251344974451E-008,-4.042717328869155E-008</div><div> 3.014026080010312E-002, 7.108929268140980E-010</div><div> 4.389283347067152E-011,-1.018558197269840E-010</div><div>-3.050731442163088E-002,-6.384100774284654E-009</div><div> 1.093044270914813E-008,-2.878418099873511E-009</div><div>-3.256726063415212E-009,-1.803331763403733E-009</div></div><div><br></div><div>...</div><div><br></div><div>------elph.1.1.xml--------<br></div><div><br></div><div>The lines after <PARTIAL_ELPH type="complex" size="289"> would be</div><div><br></div><div>the g_qν (k, i, j) for q=gamma, v=1 (first irrep) and k=gamma.</div><div><br></div><div>I guess that, since the total number of electronic bands are 17, 17x17 lines after <PARTIAL_ELPH type="complex" size="289"> are</div><div><br></div><div>g values in following order </div><div><br></div><div>band-i (initial band), band-j (final band)</div><div>1,1</div><div>2,1</div><div>3,1</div><div>...</div><div>17,1</div><div>1,2</div><div>2,2</div><div>3,2</div><div>...</div><div>17,2</div><div>...</div><div><br></div><div>is it true? </div><div><br></div><div>Finally, the values of second column for each line seem to be imaginary part of g. I am not good at quantum mechanics but i thought perturbing hamiltonian by phonon should be also hermitian and 'diagonal' element should be real number. </div><div>But in this case, there are so many indices g(q,v,i,j,k) that i cannot figure out what is 'diagonal' element of g in this case.</div><div><br></div><div><br></div><div>I apologize for ill-organized questions.<br></div><div><br></div><div>Thank you in advance. </div><div><br></div><div><br></div><div>Best regards</div><div><br></div><div>Jaehong Park</div><div><br></div>-- <br><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><font face="gulim, sans-serif" size="2">==========================================================</font></div><div><font face="gulim, sans-serif" color="#000000" size="2">Jaehong Park</font></div><div><font face="gulim, sans-serif" color="#000000" size="2">Ph.D. Candidate</font></div><div><div><font face="gulim, sans-serif" color="#000000" size="2">Dielectric Thin Film Laboratory</font></div><div><font face="gulim, sans-serif" color="#000000" size="2">Department of Materials Science & Engineering , Seoul National University</font></div></div><div><span style="color:rgb(0,0,0);font-family:gulim,sans-serif"><font size="2"><br></font></span></div><div><p style="margin:0cm 0cm 0.0001pt;text-align:justify"><span lang="EN-US"><font face="gulim, sans-serif" color="#000000" size="2">Electronic Materials Research Center</font></span></p><p style="margin:0cm 0cm 0.0001pt;text-align:justify"><span lang="EN-US"><font color="#000000" face="gulim, sans-serif">Post-Si Semiconductor Institute</font><font face="gulim, sans-serif" color="#000000" size="2"><br></font></span></p><p style="margin:0cm 0cm 0.0001pt;text-align:justify"><span lang="EN-US"><font face="gulim, sans-serif" color="#000000" size="2">Korea Institute of Science and Technology (KIST)<br>Hwarangno 14-gil, Seongbuk-gu, Seoul, 136-791, KOREA</font></span></p><p style="margin:0cm 0cm 0.0001pt;text-align:justify"><span lang="EN-US"><font face="gulim, sans-serif" color="#000000" size="2"><br></font></span></p></div><div><p style="margin:0cm 0cm 0.0001pt;text-align:justify"><span lang="EN-US"><font face="gulim, sans-serif" color="#000000" size="2">Tel : +82-2-958-6653<br><u></u></font></span></p><p style="margin:0cm 0cm 0.0001pt;text-align:justify"><span lang="EN-US"><font face="gulim, sans-serif" color="#000000" size="2">Mobile : +82-10-5481-5143</font></span></p><p style="margin:0cm 0cm 0.0001pt;text-align:justify"><span lang="EN-US"><span style="color:rgb(0,0,0);font-family:gulim,sans-serif;font-size:small;text-align:start">E-mail : <a href="mailto:catinabox@snu.ac.kr" target="_blank">catinabox@snu.ac.kr</a></span><font face="gulim, sans-serif" color="#000000" size="2"><br></font></span></p></div></div></div></div></div></div></div>
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