Fairoja
Joined: Tue Nov 20, 2018 10:43 am Posts: 4
University: Uppsala University

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.

sponce
Site Admin
Joined: Wed Jan 13, 2016 7:25 pm Posts: 569
University: Oxford

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
_________________ Dr. Samuel PoncĂ© Department of Materials University of Oxford Parks Road Oxford OX1 3PH, UK

Fairoja
Joined: Tue Nov 20, 2018 10:43 am Posts: 4
University: Uppsala University

Re: Phonon frequencies and irreducible representations
Dear Samual,
Thank you very much for the quick reply!
Best regards, Fairoja.
