Module direct 

Direct sums over cube shells, without Ewald acceleration.

Upstream: dsumsw* and dsumcw* of lattice/_dsum.pyx, with the terms _fsw* and _fcw*.

Functions

direct_shell 🔒

One unaccelerated cube shell of images, in the given lattice basis (upstream dsum*(..., i) with i = shell).

direct_term 🔒

One image of a direct sum: the outgoing wave h_l^(1)(k |r|) Y_lm(r / |r|) or H_m^(1)(k |r|) e^(i m phi) at the displacement r = -shift - R (upstream _fsw* and _fcw*). Values take special::bessel; jets take the radial jets, whose first derivative the chain rule carries. The spherical harmonic is harmonic_normalization(l, m) times the solid harmonic of the unit vector.