  MAST-SEY is an open-source Monte Carlo code capable of calculating secondary
electron emission using input data generated entirely from first principle
(density functional theory) calculations. It utilizes the complex dielectric
function and Penn's theory for inelastic scattering processes, and relativistic
Schr\"odinger theory by means of a partial-wave expansion method to govern
elastic scattering. It allows the user to include explicitly calculated
momentum dependence of the dielectric function, as well as to utilize
first-principle density of states in secondary electron generation, which
provides a more complete description of the underlying physics. In this paper
we thoroughly describe the theoretical aspects of the modeling, as used in the
code, and present sample results obtained for copper and aluminum.
