Thermal lattice expansion effect on reactive scattering of H2 from Cu(111) at T(s) = 925 K.

Surface phonons and surface temperature may have important effects on reactions of molecules at surfaces, and at present much remains unknown about these effects. A question addressed here, which has received little attention so far, is how reaction at elevated temperature is affected by thermal lattice expansion. To answer this question for the benchmark reaction of H2 and D2 with Cu(111), we have performed quantum and quasi-classical dynamics calculations. The specific reaction parameter (SRP) approach to density functional theory (DFT) has been used to compute the required six-dimensional potential energy surfaces (PES). Computed reaction probabilities and rotational quadrupole alignment parameters have been compared for surface temperatures Ts = 0 and 925 K. Surface thermal expansion of the lattice leads to a considerable decrease of reaction barrier heights and thereby to increased reaction probabilities as well as decreased rotational quadrupole alignment parameter values in associative desorption.