Matching boundary conditions (MBC's) are proposed to treat scalar
waves in the body-centered-cubic lattices. By matching the
dispersion relation, we construct MBC's for normal incidence and
incidence with an angle alpha. Multiplication of MBC operators
then leads to multi-directional absorbing boundary conditions. The
effectiveness are illustrated by the reflection coefficient analysis
and wave packet tests. In particular, the designed M1M1 treats the
scalar waves in a satisfactory manner.