A parametric study is performed to test the validity of some of the most common models of gas-surface scattering used in particle simulations of rarefied flows. The simplified models are compared with results of semiclassical molecular dynamics trajectory calculations for inelastic scattering of Xe atoms on GaSe. The simple models are shown to be inadequate to accommodate all the features of the real dynamics. Sample calculations of oxygen heterogeneous recombination on silica are also provided to emphasise the importance of vibrationally state-resolved models.