Relativistic calculations on the adsorption of CO on the (111) surfaces of Ni, Pd, and Pt within the zeroth-order regular approximation

Abstract

In this paper we first describe the implementation of the zeroth-order regular approximation ͑ZORA͒ for relativistic effects in our density-functional program for extended systems. The ZORA formalism affords approximations, which are discussed and tested, that reduce the computational effort of scalar relativistic calculations to that of nonrelativistic calculations, the inclusion of spin-orbit coupling requiring additional effort. Second, we present the outcome of nonrelativistic, scalar relativistic, and spin-orbit coupling calculations on the adsorption energy of CO on the ͑111͒ surfaces of Ni, Pd, and Pt. Relativity has a modest effect for CO on Pd, but proves to be essential for CO on Pt. The relativistic correction for the CO/Pt adsorption energy is as large as 70% at the scalar relativistic level and 55% when including spin-orbit coupling. In addition, relativity changes the preferred adsorption site for CO/Pt from hollow to top. We have examined the effects of spin polarization and of different exchange-correlation functionals, i.e., the local-density approximation ͑LDA͒ versus two generalized gradient approximations ͑GGA͒. The GGA's correct the severe overbinding by LDA of CO to the metal surfaces, and yield good agreement with experiment for adsorption energies and sites.

CO oxidation on stepped-Pt(111) under electrochemical conditions: insights from theory and experiment

“…Indeed, CO adsorption on Pt surfaces is indeed a non-trivial system to be calculated with DFT in general as the approach usually tends to overestimate the 3-fold hollow sites over atop sites, which in low temperature experiments were found to be preferred. As our aim is to investigate the co-adsorption of CO and OH, here we point the reader to the extensive discussions about the so-called "CO/Pt(111) puzzle" [41][42][43][44][45][46][47][48][49][50][51][52][53].…”

Relativistic calculations to assess the ability of the generalized gradient approximation to reproduce trends in cohesive properties of solids

“…30 Details of the implementation of this method in our bandstructure code 31 can be found in an earlier work. 32 In this context it suffices to say that it is an accurate approximation to the Dirac equation. We have employed the parametrization of Vosko and coworkers of the LDA correlation energy.…”

Reactive and diffractive scattering of H2 from Pt(111) studied using a six-dimensional wave packet method

“…33 Relativistic effects were accounted for by the zero-order regular approximation ͑ZORA͒. 34 The 6D PES ͑Ref. 35͒ was constructed from a number of 2D PESs in Z and r. Each 2D PES is a spline interpolation of 50-60 points calculated with DFT.…”