The specific reaction parameter (SRP) approach to density functional theory has been shown to model reactions of polyatomic molecules with metal surfaces important for heterogeneous catalysis in... Show moreThe specific reaction parameter (SRP) approach to density functional theory has been shown to model reactions of polyatomic molecules with metal surfaces important for heterogeneous catalysis in the industry with chemical accuracy. However, transferability of the SRP functional among systems in which methane interacts with group 10 metals remains unclear for methane + Pd(111). Therefore, in this work, predictions have been made for the reaction of CHD3 on Pd(111) using Born–Oppenheimer molecular dynamics while also performing a rough comparison with experimental data for CH4 + Pd(111) obtained for lower incidence energies. Hopefully, future experiments can test the transferability of the SRP functional among group 10 metals also for Pd(111). We found that the reactivity of CHD3 on Pd(111) is intermediate between and similar to either Pt(111) or Ni(111), depending on the incidence energy and the initial vibrational state distribution. This is surprising because the barrier height and experiments performed at lower incidence energies than investigated here suggest that the reactivity of Pd(111) should be similar to that of Pt(111) only. The relative decrease in the reactivity of Pd(111) at high incidence energies is attributed to site specificity of the reaction and to dynamical effects such as the bobsled effect and energy transfer from methane to the surface. Show less
Stepped transition metal surfaces, including the reconstructed Pt(110)-(2 × 1) surface, can be used to model the effect of line defects on catalysts. We present a combined experimental and... Show moreStepped transition metal surfaces, including the reconstructed Pt(110)-(2 × 1) surface, can be used to model the effect of line defects on catalysts. We present a combined experimental and theoretical study of CHD3 dissociation on this surface. Theoretical predictions for the initial sticking coefficients, S0, are obtained from ab initio molecular dynamics calculations using the specific reaction parameter (SRP) approach to density functional (DF) theory, while the measured sticking coefficients were obtained using the King and Wells method. The SRP DF used here had been previously derived for methane dissociation on Pt(111) so that the experiments test the transferability of this SRP DF to methane + Pt(110)-(2 × 1). The agreement between the experimental and calculated S0 is poor, with the average energy shift between the theoretical and measured reactivities being 20 kJ/mol. There are two factors which may contribute to this difference, the first of which is that there is a large uncertainty in the calculated sticking coefficients due to a large number of molecules being trapped on the surface at the end of the 1 ps propagation time. The second is that the SRP32-vdW functional may not accurately describe the Pt(110)-(2 × 1) surface. At the lowest incident energies considered here, Pt(110)-(2 × 1) is more reactive than the flat Pt(111) surface, but the situation is reversed at incident energies above 100 kJ/mol. Show less