[Pw_forum] query on e-ph tutorial

[Ajit Vallabhaneni]

Dear users,


            I have a couple of questions regarding the e-ph calculation.
1. Are the e-ph matrix element (g), coefficients lambda and gamma symmetric with respect to the phonon wave vector (q)? I mean will calculating those quantities across the IBZ sufficient to obtain the values thru out the entire BZ? 

2. In the tutorial on for calculating the "Electron-phonon interaction coefficients" on the website of QE (http://www.fisica.uniud.it/~giannozz/QE-Tutorial/tutorial_advph.html), in step 3 it was mentioned to perform an nscf calculation to prepare k and k+q wavefunctions with the keyword "calculation='phonon'". I tried to run the same, but it was termintated with the message that calculation "phonon" is not allowed. Are there any typos in this part of the example.

-bash-3.2$ pw.x < al.nscf.in

     Program PWSCF v.4.3.2      starts on 29Jan2012 at  1:21:57

     This program is part of the open-source Quantum ESPRESSO suite
     for quantum simulation of materials; please cite
         "P. Giannozzi et al., J. Phys.:Condens. Matter 21 395502 (2009);
          URL http://www.quantum-espresso.org",
     in publications or presentations arising from this work. More details at
     http://www.quantum-espresso.org/wiki/index.php/Citing_Quantum-ESPRESSO

     Parallel version (MPI), running on     1 processors

     Current dimensions of program PWSCF are:
     Max number of different atomic species (ntypx) = 10
     Max number of k-points (npk) =  40000
     Max angular momentum in pseudopotentials (lmaxx) =  3
     Waiting for input...
     Reading input from stdin

 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     from  control_checkin     : error #         1
      calculation 'phonon' not allowed
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

     stopping ...
application called MPI_Abort(MPI_COMM_WORLD, 0) - process 0



Thanks
Ajit