Function derivatives_part 

pub fn derivatives_part(
    wave: Family,
    k: Complex,
    lattice: &BlochLattice,
    shift: [f64; 3],
    eta: Complex,
    part: SumPart,
) -> Result<Derivatives>

Differentiate the selected component, holding a direct shell’s index fixed.

Errors

As sum, and Error::InvalidInput for the real or reciprocal part at eta = 0, whose split derivative needs an explicit split.