Optimized spherical Bessel representation for dummy atoms on a regular grid
In dummy atom models where the atoms are on a regular lattice, the squared distance to the origin is always an integer multiple of the (squared) lattice vector. If a non-uniform
s axis is used such that
s^2 is linearly spaced, the
r s values of all atoms will line up so that many values are shared between atoms and only need to be calculated once.