NLSPLINE

NLSPLINE = .TRUE. | .FALSE.
Default: NLSPLINE = .FALSE.

Description: construct the PAW projectors in reciprocal space using spline interpolation so that they are k-differentiable.

For NLSPLINE=.TRUE., the PAW projectors in reciprocal space (LREAL=.FALSE.) are set up using a spline interpolation so that they are k differentiable. This improves the susceptibility contribution to the chemical shifts. It only slightly affects the other contributions to the chemical shifts.

It is advised to set NLSPLINE=.TRUE. if and only if PAW projectors are applied in reciprocal space and chemical shifts are calculated, i.e., if and only if LREAL=.FALSE. and LCHIMAG=.TRUE. As this option also gives slightly different total energies, it is advised to use the default NLSPLINE=.FALSE. in all other calculations for reasons of compatibility.

Real-space projectors are k differentiable by construction, hence do not require to set NLSPLINE=.TRUE.

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