Gas sorption in solid surfaces: a computational study using rigid and Einstein-solid models

The reactive Monte Carlo (RxMC) method was proposed to describe the sorption of gases in solid materials due to the chemical reaction A + B ⇌ C. Two models were used to simulate the solid; the first model considered simulations with rigid particles in the solid whereas in the second model the particles were allowed to vibrate inside the solid with a given spring constant, i.e. an Einstein solid was used to simulate the substrate. In both models not only physisorption but also chemisorption of the fluid was observed. Sorption curves, at different spring constants, were simulated and it was noted that sorption was always enhanced with the Einstein solid model. Moreover, an inverse dependent function of the spring constant with the temperature was found. Finally, the second model might be used to explain the unusual sorption behavior observed in actual experimental reactions such as CO2 + Li2O ⇌ Li2CO3.