ODDONLY

ODDONLY = .TRUE. | .FALSE.
Default: ODDONLY = .FALSE.

Description: ODDONLY=.TRUE. selects a subset of k-points for the representation of the Fock exchange potential, with C₁=C₂=C₃=1, and n₁+n₂+n₃ odd.

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

\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.

ODDONLY=.TRUE. selects a subset of k-points with C₁=C₂=C₃=1, and n₁+n₂+n₃ odd. It reduces the computational work load for HF type calculations by a factor two, but is only sensible for high symmetry cases (such as sc, fcc or bcc cells).

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

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