The kernels of the Orbital FTs as defined in Equation
may be calculated analytically as an integral over the angular polar
coordinates.
The s spherical harmonic
which has no angular dependence
gives rise to the simplest kernel
Higher order spherical harmonics give rise to more complex kernels,
for example
gives
Here
, and similarly we define
and
.
The kernels of spherical harmonics with non-zero m must be
constructed by finding the kernels corresponding to linear
combinations of spherical harmonics with equal l and m of equal
magnitude, but opposite sign. These combinations are constructed such
that the expressions generated are either purely imaginary or
real. The kernels of these linear combinations may then be combined to
generate the kernels corresponding to the original spherical harmonic.
For example the
and
kernels may be found as
follows:
The kernels
and
may be found in the same way as
above and are:
Therefore
and
are given by
The kernels for the d orbitals may be calculated in a similar way and are;
where
,
, etc.