Thus a greater Sn fraction in the alloyed composition is predicted to yield increased stability with respect to decomposition in air and water, as witnessed experimentally. While empirically we expect more rapid decomposition with more exothermic (negative) reaction energies, we note that these calculations do not account for reaction kinetics. The hygroscopic nature of these compounds suggests that surface hydration could have a catalytic effect on decomposition rates, contributing to the accelerated decomposition in humid environments.