Forum EPWhttp://epwforum.uk/ Phonon frequencies and irreducible representationshttp://epwforum.uk/viewtopic.php?f=7&t=730 Page 1 of 1

 Author: Fairoja [ Tue Nov 20, 2018 12:11 pm ] Post subject: Phonon frequencies and irreducible representations Dear All,I am trying to compute the electron-phonon coupling matrix for an 8 atom cell using ph.x with k-grid of 12x12x6 and q-point 4x4x2.I am computing each of the 12 q-points separately. For the first q-point (gamma-point), the system has 16 irreps. From the output file one can get all the mode symmetries for each irrep and corresponding frequencies, as shown below:------------------------------------------------------------------------ Mode symmetry, D_4h(4/mmm) point group: Atomic displacements: There are 16 irreducible representations Representation 1 1 modes -A_1g X_1 M_1 Done Representation 2 1 modes -A_1g X_1 M_1 Done Representation 3 1 modes -B_1g X_2 M_2 Done Representation 4 1 modes -B_1g X_2 M_2 Done Representation 5 2 modes -E_g X_5 M_5 Done Representation 6 2 modes -E_g X_5 M_5 Done Representation 7 2 modes -E_g X_5 M_5 Done Representation 8 2 modes -E_g X_5 M_5 Done Representation 9 1 modes -A_2u X_4' M_4' Done Representation 10 1 modes -A_2u X_4' M_4' Done Representation 11 1 modes -A_2u X_4' M_4' Done Representation 12 1 modes -A_2u X_4' M_4' Done Representation 13 2 modes -E_u X_5' M_5' Done Representation 14 2 modes -E_u X_5' M_5' Done Representation 15 2 modes -E_u X_5' M_5' Done Representation 16 2 modes -E_u X_5' M_5' Done q = ( 0.000000000 0.000000000 0.000000000 ) ************************************************************************** freq ( 1) = -0.143039 [THz] = -4.771283 [cm-1] freq ( 2) = 0.141240 [THz] = 4.711264 [cm-1] freq ( 3) = 0.141240 [THz] = 4.711264 [cm-1] freq ( 4) = 1.868022 [THz] = 62.310502 [cm-1] freq ( 5) = 1.868022 [THz] = 62.310502 [cm-1] freq ( 6) = 2.532549 [THz] = 84.476756 [cm-1] freq ( 7) = 3.475908 [THz] = 115.943802 [cm-1] freq ( 8) = 3.475908 [THz] = 115.943802 [cm-1] freq ( 9) = 4.146052 [THz] = 138.297422 [cm-1] freq ( 10) = 4.146052 [THz] = 138.297422 [cm-1] freq ( 11) = 5.200291 [THz] = 173.463047 [cm-1] freq ( 12) = 5.934808 [THz] = 197.963889 [cm-1] freq ( 13) = 6.503338 [THz] = 216.928000 [cm-1] freq ( 14) = 7.792651 [THz] = 259.934858 [cm-1] freq ( 15) = 8.280964 [THz] = 276.223233 [cm-1] freq ( 16) = 8.280964 [THz] = 276.223233 [cm-1] freq ( 17) = 8.684696 [THz] = 289.690268 [cm-1] freq ( 18) = 8.684696 [THz] = 289.690268 [cm-1] freq ( 19) = 10.769522 [THz] = 359.232578 [cm-1] freq ( 20) = 11.594174 [THz] = 386.740014 [cm-1] freq ( 21) = 11.594174 [THz] = 386.740014 [cm-1] freq ( 22) = 15.172169 [THz] = 506.089090 [cm-1] freq ( 23) = 16.389027 [THz] = 546.679088 [cm-1] freq ( 24) = 16.389027 [THz] = 546.679088 [cm-1] ************************************************************************** Mode symmetry, D_4h(4/mmm) point group: freq ( 1 - 1) = -4.8 [cm-1] --> A_2u X_4' M_4' I freq ( 2 - 3) = 4.7 [cm-1] --> E_u X_5' M_5' I freq ( 4 - 5) = 62.3 [cm-1] --> E_u X_5' M_5' I freq ( 6 - 6) = 84.5 [cm-1] --> A_2u X_4' M_4' I freq ( 7 - 8) = 115.9 [cm-1] --> E_g X_5 M_5 R freq ( 9 - 10) = 138.3 [cm-1] --> E_g X_5 M_5 R freq ( 11 - 11) = 173.5 [cm-1] --> A_1g X_1 M_1 R freq ( 12 - 12) = 198.0 [cm-1] --> A_1g X_1 M_1 R freq ( 13 - 13) = 216.9 [cm-1] --> B_1g X_2 M_2 R freq ( 14 - 14) = 259.9 [cm-1] --> A_2u X_4' M_4' I freq ( 15 - 16) = 276.2 [cm-1] --> E_u X_5' M_5' I freq ( 17 - 18) = 289.7 [cm-1] --> E_g X_5 M_5 R freq ( 19 - 19) = 359.2 [cm-1] --> B_1g X_2 M_2 R freq ( 20 - 21) = 386.7 [cm-1] --> E_u X_5' M_5' I freq ( 22 - 22) = 506.1 [cm-1] --> A_2u X_4' M_4' I freq ( 23 - 24) = 546.7 [cm-1] --> E_g X_5 M_5 R electron-phonon interaction ...--------------------------------------------------------------------------By comparing the Raman modes of point groups, I can identify the corresponding frequencies and thereby elph.#iq.#irr.xml File (there are 16 elph.#iq.#irr.xml files).The next q-point (0.000000000 0.000000000 -0.239442795) also has 16 irreps, but the Raman modes are not specified in this case;------------------------------------------------------------------------- Atomic displacements: There are 16 irreducible representations Representation 1 2 modes - Done Representation 2 2 modes - Done Representation 3 2 modes - Done Representation 4 1 modes - Done Representation 5 1 modes - Done Representation 6 1 modes - Done Representation 7 2 modes - Done Representation 8 2 modes - Done Representation 9 1 modes - Done Representation 10 1 modes - Done Representation 11 1 modes - Done Representation 12 2 modes - Done Representation 13 1 modes - Done Representation 14 2 modes - Done Representation 15 2 modes - Done Representation 16 1 modes - Done q = ( 0.000000000 0.000000000 -0.239442795 ) ************************************************************************** freq ( 1) = 1.057811 [THz] = 35.284761 [cm-1] freq ( 2) = 1.057811 [THz] = 35.284761 [cm-1] freq ( 3) = 1.480778 [THz] = 49.393431 [cm-1] freq ( 4) = 1.536907 [THz] = 51.265692 [cm-1] freq ( 5) = 1.536907 [THz] = 51.265692 [cm-1] freq ( 6) = 2.357932 [THz] = 78.652135 [cm-1] freq ( 7) = 3.508436 [THz] = 117.028814 [cm-1] freq ( 8) = 3.508436 [THz] = 117.028814 [cm-1] freq ( 9) = 4.136431 [THz] = 137.976482 [cm-1] freq ( 10) = 4.136431 [THz] = 137.976482 [cm-1] freq ( 11) = 5.311737 [THz] = 177.180465 [cm-1] freq ( 12) = 5.687131 [THz] = 189.702287 [cm-1] freq ( 13) = 6.580806 [THz] = 219.512069 [cm-1] freq ( 14) = 7.755222 [THz] = 258.686350 [cm-1] freq ( 15) = 8.278951 [THz] = 276.156083 [cm-1] freq ( 16) = 8.278951 [THz] = 276.156083 [cm-1] freq ( 17) = 8.666585 [THz] = 289.086145 [cm-1] freq ( 18) = 8.666585 [THz] = 289.086145 [cm-1] freq ( 19) = 10.777740 [THz] = 359.506708 [cm-1] freq ( 20) = 11.612857 [THz] = 387.363206 [cm-1] freq ( 21) = 11.612857 [THz] = 387.363206 [cm-1] freq ( 22) = 15.267973 [THz] = 509.284772 [cm-1] freq ( 23) = 16.394501 [THz] = 546.861684 [cm-1] freq ( 24) = 16.394501 [THz] = 546.861684 [cm-1] ************************************************************************** electron-phonon interaction ...-------------------------------------------------------------------------I was using the same version on the same computer. On the latter case, I can't identify the frequencies corresponding to elph.#iq.#irr.xml files. Out of 12 q-points Raman modes are specified only on 5 of them. Please help me to solve this. Or any other method to get the frequencies corresponding to each irrep.Thank you for your time and consideration,Best regards,Fairoja.-----------Fairoja Cheenicode KabeerPostdoctoral researcher,Materials Theory,Uppsala University,Uppsala, Sweden.

 Author: sponce [ Thu Nov 22, 2018 10:29 am ] Post subject: Re: Phonon frequencies and irreducible representations Dear Fairoja, It seems you are using the phonon code ph.x (i.e. not the EPW code). Therefore such question might be best asked on the Quantum Espresso mailing list. The expert for this should be Prof. Andrea Dal Corso.Best wishes, Samuel

 Author: Fairoja [ Fri Nov 23, 2018 11:35 pm ] Post subject: Re: Phonon frequencies and irreducible representations Dear Samual,Thank you very much for the quick reply!Best regards,Fairoja.

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