distance between grid points for non local potential
These tags determine the grid for the non local potential in reciprocal space.
If you want to avoid incompatibilities with VAMP, NQNL must be 100,
this is also the default value.
Default for DELQNL is 0.1, the actual spacing is 2/RCORE DELQNL 1/a.u.,
NQNNL is only used in conjunction with perturbation theory.
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