Compactness and d-band filling effect on chemical descriptors for transition metals

Abstract

This project bases on the study of the d-band center, the width corrected d-band center, and the maximum point of the Hilbert transform of the d-band as a chemical descriptors for the activity of the hexagonal close packed (hcp) transition metal (0001), (101􀴤 0), and (112􀴤 0) surfaces. It has been carried out by computational simulations using Density Functional Theroy (DFT) with the Perdew-Burke-Ernzerhof (PBE) and Tao-Perdew-Staroverov-Scuseria (TPSS) approximations for the exchange and correlation functional. To do so, first, cohesive energies and shortest internuclear distances have been calculated for bulk hcp, and compared with previous calculations and experimental data to validate the computational setups. The surfaces have been simulated and some surface properties have been compared with experimental data. These are the fixed surface energy, the relaxed surface energy, and the relaxation energy, as well as the structural surface relaxation. The density of states of each surface has been acquired to obtain estimates of the above commented descriptors. These values have been examined on their capacity to describe the metallic surfaces activity comparing the results to literature available adsorption energies. The descriptor with best agreement with adsorption energies is the original d-band center, as the other two descriptors do not add any additional beneficial information to the d-band, given that their trends on adsorption energies are worse.