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# EVENONLY

EVENONLY = .TRUE. | .FALSE.
Default: EVENONLY = .FALSE.

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

One may restrict the sum over q in the Fock exchange potential (or one of its short range counterparts) to a subset, {qk}, of the full (N1×N2×N3) k-point set, {k}, for which the following holds

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

where b1,2,3 are the reciprocal lattice vectors of the primitive cell, and Ci is the integer grid reduction factor along reciprocal lattice direction bi.

EVENONLY=.TRUE. selects a subset of k-points with C1=C2=C3=1, and n1+n2+n3 even. 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).