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Dear All,

I am calculating on the complex dielectric tensor (cartesian coordinates) of alpha-PbO with the BS equation. I can not obtain the dielectric complex tensor after the successful BSE calculation. It is said "Subroutine Unknown:0:COMMENT The EXC dielectric complex tensor cannot be computed There must be 6 different q-points in long wavelength limit (see gw_nqlwl)" in log file. The alpha-PbO is tetragonal crystal system, whose rprim is unity matrix. There are only 3 independent q-points below "List of q-points for the optical limit"in "*EXC_MDF" file. I think this is the reason why I can not obtain the dielectric complex tensor by default settings of "gw_nqlwl" and "gw_qlwl".

So, I have two questions:
1> how I define "gw_nqlwl" and "gw_qlwl" by hand if I want to obtain the complex dielectric tensor (cartesian coordinates) of alpha-PbO?
2> The two manual input variables are only required for "optdriver=99"? or required for both "optdriver=99" and "optdriver=3"?

Any help on the above will be highly appreciated.

Best regards,
Gao Tang

Hi
I used the below parameters to meet the requirements of BSE calculation (optdriver=99) for dielectric complex tensor output, and it worked.

gw_qlwl
1.0, 0.0, 0.0
0.0, 1.0, 0.0
0.0, 0.0, 1.0
0.0, 0.5, 0.5
0.5, 0.0, 0.5
0.5, 0.5, 0.0
gw_nqlwl 6


Gao