NKREDZ

NKREDZ = [integer]
Default: NKREDZ = 1

Description: NKREDZ specifies a reduction factor for the q-point grid representation of the exact exchange potential along reciprocal space direction b₃.

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 (N₁×N₂×N₃) k-point set, {k}, for which the following holds

q_{𝐤} = 𝐛_{1} \frac{n_{1} C_{1}}{N_{1}} + 𝐛_{2} \frac{n_{2} C_{2}}{N_{2}} + 𝐛_{3} \frac{n_{3} C_{3}}{N_{3}}, (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 C₁=C₂=C₃=NKRED. If one wants to specify separate grid reduction factors for C₁, C₂, and C₃ one should use C₁=NKREDX, C₂=NKREDY, and C₃=NKREDZ, respectively.

Warning: there are circumstances under which NKRED and NKREDX,Y,Z should not be used!

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