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Phonon frequencies and irreducible representations http://epwforum.uk/viewtopic.php?f=7&t=730 
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Author:  Fairoja [ Tue Nov 20, 2018 12:11 pm ] 
Post subject:  Phonon frequencies and irreducible representations 
Dear All, I am trying to compute the electronphonon coupling matrix for an 8 atom cell using ph.x with kgrid of 12x12x6 and qpoint 4x4x2. I am computing each of the 12 qpoints separately. For the first qpoint (gammapoint), 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 [cm1] freq ( 2) = 0.141240 [THz] = 4.711264 [cm1] freq ( 3) = 0.141240 [THz] = 4.711264 [cm1] freq ( 4) = 1.868022 [THz] = 62.310502 [cm1] freq ( 5) = 1.868022 [THz] = 62.310502 [cm1] freq ( 6) = 2.532549 [THz] = 84.476756 [cm1] freq ( 7) = 3.475908 [THz] = 115.943802 [cm1] freq ( 8) = 3.475908 [THz] = 115.943802 [cm1] freq ( 9) = 4.146052 [THz] = 138.297422 [cm1] freq ( 10) = 4.146052 [THz] = 138.297422 [cm1] freq ( 11) = 5.200291 [THz] = 173.463047 [cm1] freq ( 12) = 5.934808 [THz] = 197.963889 [cm1] freq ( 13) = 6.503338 [THz] = 216.928000 [cm1] freq ( 14) = 7.792651 [THz] = 259.934858 [cm1] freq ( 15) = 8.280964 [THz] = 276.223233 [cm1] freq ( 16) = 8.280964 [THz] = 276.223233 [cm1] freq ( 17) = 8.684696 [THz] = 289.690268 [cm1] freq ( 18) = 8.684696 [THz] = 289.690268 [cm1] freq ( 19) = 10.769522 [THz] = 359.232578 [cm1] freq ( 20) = 11.594174 [THz] = 386.740014 [cm1] freq ( 21) = 11.594174 [THz] = 386.740014 [cm1] freq ( 22) = 15.172169 [THz] = 506.089090 [cm1] freq ( 23) = 16.389027 [THz] = 546.679088 [cm1] freq ( 24) = 16.389027 [THz] = 546.679088 [cm1] ************************************************************************** Mode symmetry, D_4h(4/mmm) point group: freq ( 1  1) = 4.8 [cm1] > A_2u X_4' M_4' I freq ( 2  3) = 4.7 [cm1] > E_u X_5' M_5' I freq ( 4  5) = 62.3 [cm1] > E_u X_5' M_5' I freq ( 6  6) = 84.5 [cm1] > A_2u X_4' M_4' I freq ( 7  8) = 115.9 [cm1] > E_g X_5 M_5 R freq ( 9  10) = 138.3 [cm1] > E_g X_5 M_5 R freq ( 11  11) = 173.5 [cm1] > A_1g X_1 M_1 R freq ( 12  12) = 198.0 [cm1] > A_1g X_1 M_1 R freq ( 13  13) = 216.9 [cm1] > B_1g X_2 M_2 R freq ( 14  14) = 259.9 [cm1] > A_2u X_4' M_4' I freq ( 15  16) = 276.2 [cm1] > E_u X_5' M_5' I freq ( 17  18) = 289.7 [cm1] > E_g X_5 M_5 R freq ( 19  19) = 359.2 [cm1] > B_1g X_2 M_2 R freq ( 20  21) = 386.7 [cm1] > E_u X_5' M_5' I freq ( 22  22) = 506.1 [cm1] > A_2u X_4' M_4' I freq ( 23  24) = 546.7 [cm1] > E_g X_5 M_5 R electronphonon 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 qpoint (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 [cm1] freq ( 2) = 1.057811 [THz] = 35.284761 [cm1] freq ( 3) = 1.480778 [THz] = 49.393431 [cm1] freq ( 4) = 1.536907 [THz] = 51.265692 [cm1] freq ( 5) = 1.536907 [THz] = 51.265692 [cm1] freq ( 6) = 2.357932 [THz] = 78.652135 [cm1] freq ( 7) = 3.508436 [THz] = 117.028814 [cm1] freq ( 8) = 3.508436 [THz] = 117.028814 [cm1] freq ( 9) = 4.136431 [THz] = 137.976482 [cm1] freq ( 10) = 4.136431 [THz] = 137.976482 [cm1] freq ( 11) = 5.311737 [THz] = 177.180465 [cm1] freq ( 12) = 5.687131 [THz] = 189.702287 [cm1] freq ( 13) = 6.580806 [THz] = 219.512069 [cm1] freq ( 14) = 7.755222 [THz] = 258.686350 [cm1] freq ( 15) = 8.278951 [THz] = 276.156083 [cm1] freq ( 16) = 8.278951 [THz] = 276.156083 [cm1] freq ( 17) = 8.666585 [THz] = 289.086145 [cm1] freq ( 18) = 8.666585 [THz] = 289.086145 [cm1] freq ( 19) = 10.777740 [THz] = 359.506708 [cm1] freq ( 20) = 11.612857 [THz] = 387.363206 [cm1] freq ( 21) = 11.612857 [THz] = 387.363206 [cm1] freq ( 22) = 15.267973 [THz] = 509.284772 [cm1] freq ( 23) = 16.394501 [THz] = 546.861684 [cm1] freq ( 24) = 16.394501 [THz] = 546.861684 [cm1] ************************************************************************** electronphonon 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 qpoints 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 Kabeer Postdoctoral 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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