# [Pw_forum] Query on "e-ph interaction coefficients

Ajit Vallabhaneni avallabh at purdue.edu
Mon Nov 28 01:19:00 CET 2011

```Dear users,

I had recently started working on Quantum espresso. I was doing the tutorials on e-ph interaction coeff's tutorial on aluminium. I ran the simulation at point X. The following is a part of the output in which i want to know what few things represent.

- what does the two irreducible representations mean ? It shows that it is related to atomic displacements, but i could not see what does the terms "Representation  1 1 modes -A_2u X_4' M_4' To be done " means and what does the term 1 modes  and 2 modes stand for ?

Thanks
Ajit

************************************************************************************
Atomic displacements:
There are   2 irreducible representations

Representation     1      1 modes -A_2u X_4' M_4' To be done

Representation     2      2 modes -E_u  X_5' M_5' To be done

Representation #  1 mode #   1

Self-consistent Calculation

iter #   1 total cpu time :    27.1 secs   av.it.:   3.9
thresh= 0.100E-01 alpha_mix =  0.700 |ddv_scf|^2 =  0.735E-04

iter #   2 total cpu time :    28.0 secs   av.it.:   5.4
thresh= 0.857E-03 alpha_mix =  0.700 |ddv_scf|^2 =  0.311E-04

iter #   3 total cpu time :    29.0 secs   av.it.:   5.1
thresh= 0.558E-03 alpha_mix =  0.700 |ddv_scf|^2 =  0.526E-08

iter #   4 total cpu time :    29.9 secs   av.it.:   5.4
thresh= 0.725E-05 alpha_mix =  0.700 |ddv_scf|^2 =  0.289E-10

iter #   5 total cpu time :    30.8 secs   av.it.:   5.1
thresh= 0.537E-06 alpha_mix =  0.700 |ddv_scf|^2 =  0.779E-14

End of self-consistent calculation

Convergence has been achieved

Representation #  2 modes #   2  3

Self-consistent Calculation

iter #   1 total cpu time :    33.4 secs   av.it.:   3.5
thresh= 0.100E-01 alpha_mix =  0.700 |ddv_scf|^2 =  0.298E-06

iter #   2 total cpu time :    35.4 secs   av.it.:   6.2
thresh= 0.546E-04 alpha_mix =  0.700 |ddv_scf|^2 =  0.406E-08

iter #   3 total cpu time :    37.3 secs   av.it.:   5.7
thresh= 0.637E-05 alpha_mix =  0.700 |ddv_scf|^2 =  0.401E-09

iter #   4 total cpu time :    39.2 secs   av.it.:   5.5
thresh= 0.200E-05 alpha_mix =  0.700 |ddv_scf|^2 =  0.119E-13

iter #   5 total cpu time :    41.3 secs   av.it.:   6.4
thresh= 0.109E-07 alpha_mix =  0.700 |ddv_scf|^2 =  0.471E-15

End of self-consistent calculation

Convergence has been achieved

Number of q in the star =    3
List of q in the star:
1   0.000000000   0.000000000   1.000000000
2   0.000000000   1.000000000   0.000000000
3   1.000000000   0.000000000   0.000000000

Diagonalizing the dynamical matrix

q = (    0.000000000   0.000000000   1.000000000 )

**************************************************************************
omega( 1) =       6.001070 [THz] =     200.174161 [cm-1]
omega( 2) =       6.001070 [THz] =     200.174161 [cm-1]
omega( 3) =       9.595361 [THz] =     320.066785 [cm-1]
**************************************************************************

Mode symmetry, D_4h(4/mmm) point group:

omega(  1 -  2) =        200.2  [cm-1]   --> E_u  X_5' M_5'
omega(  3 -  3) =        320.1  [cm-1]   --> A_2u X_4' M_4'

**************************************************************************

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