Theoretical study of the H/D isotope effect of CH4/CD4 adsorption on a Rh(111) surface using a combined plane wave and localized basis sets method

We analysed the H/D isotope effect of CH₄/CD₄ adsorption on a Rh(111) surface using our combined plane wave and localized basis sets method, that we proposed for the consideration of delocalized electrons on a surface and the quantum effect of protons (deuterons) in metal–molecule interactions. We observed that the adsorption distance and energy of CD₄ were larger and lower than those of CH₄, respectively. This is in reasonable agreement with the corresponding experimental results of cyclohexane adsorption. We clearly found that the trend of the H/D isotope effect in the geometrical and energetic difference was similar to that of the hydrogen-bonded systems.

Using our CPLB method, we elucidate that the adsorption distance and adsorption energy of CH₄ on the Rh(111) surface are shorter and larger than those of CD₄, which is in reasonable agreement with the corresponding H/D isotope trend in experiments.