[Pw_forum] electron phonon calculation at the Gamma point

[Elie M]

Dear all,
I am trying to do el-ph calculations only at the Gamma point for graphene (as I want to compare it to another system where the calculations are only feasible at the Gamma point). However the values I am getting for lambda for graphene  AT THE GAMMA POINT are really high:
degauss   lambda    

  0.005  
13.442600   0.015    2.303600   0.020    1.756000   

  0.025   
1.436000    

  0.030   
1.228800    

  0.035   
1.085800    

  0.040   
0.983000    

  0.045   
0.906400    

 
0.050    0.847800I am using a 90 x90 x1 grid (in scf) for graphene. 
It is already known that lambda for graphene is  ~0.02. (1) Do the above results mean that one cannot calculate el-ph coefficients unless on a grid of phonons and then are the calculations -at the Gamma point ONLY- useless and unexact?
(2) or does this mean that the results did not converge due to a small k-mesh in the scf calculations (90x90x1) and I need to increase it to say 400x400x1?
Any suggestions of any kind would also be ahighly appreciated.
Thanks for your help
Elie MUniversity of NottsNG7 2RDUK

     		 	   		  
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