Error in routine ktokpmq

[Akshay]

Hi,
I am performing an electron-phonon calculation in EPW 6.1. During the calculation I encounter the following error:
{Error in routine ktokpmq (1):
coarse k-mesh needs to be strictly positive in 1st BZ}
My current coarse grids are,
nk1 = 12
nk2 = 12
nk3 = 12

nq1 = 6
nq2 = 6
nq3 = 6
The 12×12×12 k-grid is commensurate with the 6×6×6 q-grid. I understand from the ktokpmq routine that EPW requires the coarse k-points to be represented with positive crystal coordinates within the first Brillouin zone, i.e. in the range [0,1). therefore generated the 12×12×12 k-point mesh using the Wannier90 kmesh.pl utility uniformly. However, I still encounter the same ktokpmq error in EPW. Please find the attachment.
Looking forward your responses.
Thanks!
Akshay Kumar Majee,
NISER Bhubaneswar, India

[stiwari]

Hello Akshay,

This issue appears when you use more cores (npool) than total number of k-points, 1728 in your case. It can also appear if you use SCF wavefunctions within the 1st BZ for the EPW calculation instead of NSCF wavefunctions on a uniform grid.

Best regards,
Sabya.