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 C ₁=NKREDX, C ₂=NKREDY, and C ₃=NKREDZ, respectively.

Related Tags and Sections

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

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