[QE-developers] KCW: doubled nkstot after q /= 0 nscf calculation

[Jacob Williams]

Dear all,

I am working on the LOSC correction for DFT (extending doi:10.1103/PhysRevB.106.035147), with code that modifies the KCW module from QE 7.1. So, first, I’d like to thank the developers of KCW for their excellent work and for discovering a primitive-cell-periodic way to handle Wannier function densities, which had troubled my collaborator and me for some years.

I need to use nkstot == nk1 * nk2 * nk3 * nspin as part of the calculation analogous to screen_coeff.f90, after the Sternheimer equation calculations are finished. However, when nk1, nk2, and nk3 are all greater than 1, it seems that the routine kcw_run_nscf(), or perhaps the linear-response calculation of alpha, recalculates nkstot and in particular doubles it for q /= 0. (I can find this by printing nkstot to standard output at lines 108 and 253 respectively of KCW/src/screen_coeff.f90 and then executing KCW/examples/example01/run_example; I find that before the linear response calculation nkstot = 16, but after nkstot = 32.) Could you enlighten me as to why this change to nkstot occurs?

Sincerely yours,

Jacob Williams
Ph.D. candidate, Yang group
Vice President, Graduate Chemistry Council
Duke University Department of Chemistry
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