NKRED

NKRED = [integer]
Default: NKRED = 1 

Description: NKRED specifies an uniform reduction factor for the q-point grid representation of the exact exchange potential.

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One may restrict the sum over q in the Fock exchange potential (or one of its short range counterparts) to a subset, {q_k}, of the full (N ₁×N ₂×N ₃) k-point set, {k}, for which the following holds

$\mathbf {q_{k}} =\mathbf {b} _{1}{\frac {n_{1}C_{1}}{N_{1}}}+\mathbf {b} _{2}{\frac {n_{2}C_{2}}{N_{2}}}+\mathbf {b} _{3}{\frac {n_{3}C_{3}}{N_{3}}},\quad (n_{i}=0,..,N_{i}-1)$

where b_1,2,3 are the reciprocal lattice vectors of the primitive cell, and C _i is the integer grid reduction factor along reciprocal lattice direction b _i. This leads to a reduction in the computational workload by a factor:

${\frac {1}{C_{1}C_{2}C_{3}}}$

In case one sets NKRED, the grid reduction factors will be uniformly set to C ₁=C ₂=C ₃=NKRED. If one wants to specify separate grid reduction factors for C ₁, C ₂, and C ₃ one should use NKREDX, NKREDY, and NKREDZ, respectively.

Related Tags and Sections

NKREDX, NKREDY, NKREDZ, EVENONLY, ODDONLY, downsampling, Hartree-Fock_and_HF/DFT_hybrid_functionals

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