  We determine two-particle scattering phase shifts and mixing angles for
quantum theories defined with lattice regularization. The method is suitable
for any nonrelativistic effective theory of point particles on the lattice. In
the center-of-mass frame of the two-particle system we impose a hard spherical
wall at some fixed large radius. For channels without partial-wave mixing the
partial-wave phase shifts are determined from the energies of the
nearly-spherical standing waves. For channels with partial-wave mixing further
information is extracted by decomposing the standing wave at the wall boundary
into spherical harmonics, and we solve coupled-channels equations to extract
the phase shifts and mixing angles. The method is illustrated and tested by
computing phase shifts and mixing angles on the lattice for spin-1/2 particles
with an attractive Gaussian potential containing both central and tensor force
parts.
