The atomistic model of amorphous silicon carbide membrane that was developed in Parts l and II of this series is utilized in nonequilibrium molecular dynamics (MD) simulations to study transport and separation of equimolar gaseous mixtures H-2/CO2 and H-2/CH4 in the membrane at high temperatures. We simulated membranes with up to about 39 fin in thickness, containing up to 170,000 atoms, and up to 100 on to obtain reliable statistics. The effect of parameters such as the temperature, the applied pressure drop across the system, and the membrane's thickness on the separation properties was studied. The trends in the dependence of the separation factor on the membrane's thickness are consistent with experiments, namely the separation factor increases with the thickness up to an optimal value, beyond which it remains constant, or may even decrease. The dependence of the computed separation factor on the membrane's thickness is used in conjunction with the experimental values of the separation factor to estimate the thickness of actual membranes. The results are in agreement with the experimental data, demonstrating the value of MD simulations with a reactive force field for characterizing the properties of complex amorphous films, and flow and transport therein. (C) 2014 Elsevier B.V. All rights reserved,