Toward accurate reaction energetics for molecular line growth at surface: Quantum Monte Carlo and density functional theory calculations

We revisit the molecular line growth mechanism of styrene on the hydrogenated Si (001) 2 X 1 surface. In particular, we investigate the energetics of the radical chain reaction mechanism by means of diffusion quantum Monte Carlo (QMC) and density functional theory (DFT) calculations. For the exchange correlation (XC) functional we use the nonempirical generalized-gradient approximation (GGA) and meta-GGA. We find that the QMC result also predicts the intra-dimer-row growth of the molecular line over the inter-dimer-row growth, supporting the conclusion based on DFT results. However, the absolute magnitudes of the adsorption/reaction energies and the heights of the energy barriers differ considerably between the QMC and DFT with the GGA/meta-GGA XC functionals. (C) 2009 American Institute of Physics. [doi:10.1063/1.3265768]