[Pw_forum] ele phonon coupling at the gamma point
Elie M
elie.moujaes at hotmail.co.uk
Tue Oct 2 18:42:58 CEST 2012
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 :
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 and the ph file has only one point nq1=0 nq2=0, nq3=0 (the Gamma point).
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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