Due to the large concentration of electrically active defects in Hg1-xCdxTe, it is important to properly account for them when designing fabrication processes for infrared focal plane arrays (IRFPAs). Stanford University's Mercury Cadmium Telluride Process Simulator, SUMerCad, is being developed to simulate the interaction of native defects and dopants in Hg0.8Cd0.2Te in order to accurately model various processing techniques. Non-linear coupled differential equations are used to model the physics of the diffusion mechanisms, rather than extrapolating the diffusion profiles from experimental data. The fundamental constants for the point defects were obtained by exercising the simulator over the various parameter spaces and comparing the results to experimental work and best principle calculations. The methodologies used, point defect mechanisms modeled, and parameters determined are discussed.