EPW Forum

Dear epw users

I am trying to do epw calculations for Pb. At first, phonon calculation with 8*8*8 (after one scf calculation with 16*16*!6*!*!*1) and then in the epw step I did one scf (8*8*8*1*1*1) and later on a nscf (216 points) calculation and finally epw.in (with nkf1=nkf2=nkf3=20 and nqf1=nqf2=nqf3=20 and nk1=nk2=nk3=6 and nq1=nq2=nq3=8)

However, my epw.x run has failed with this error in CRASH file:
task # 0
from createkmap : error # 1
q-vec not commensurate


I would be very thankful if somebody could help me
Best regards
Amir T

Dear Amir T:

As the error message says, the q grid should be commensurate with the k grid when using the uniform grids in EPW [J. Noffsinger et al, Comput. Phys. Comm. 181, 2140 (2010)].
That is, for the coarse grids, you should use nk1=nk2=nk3=16 or nk1=nk2=nk3=8 with nq1=nq2=nq3=8, etc. (nk* should be equal to or larger than nq*.)

Sincerely,

H. Lee