Structure of the Au/Pd(100) Alloy Surface

Abstract

The distribution of gold atoms on the surface of a Au/Pd(100) alloy with various gold coverages was explored using density functional theory (DFT) calculations and measurements of the low-energy electron diffraction (LEED) patterns. DFT calculation revealed the presence of first-, second-, and third-neighbor interactions. This contrasts the behavior of Au/Pd(111) alloys, where there were only nearest-neighbor interactions between the surface gold and palladium atoms. The presence of longer-range interactions was confirmed by LEED, which showed c(2 × 2) structures for palladium coverages between 0.5 and ∼0.75 monolayers (ML) and a (3 × 3) pattern between 0.5 and ∼0.85 ML. The surface structure was simulated using first-, second-, and third-neighbor interactions using Monte Carlo methods and was successfully able to reproduce the experimentally observed LEED patterns. The simulations were then used to calculate the variation in coverage of bridge-bonded carbon monoxide on the Au/Pd(100) alloy as a function of alloy composition, which also agreed well with experiment.