Quantum Monte Carlo simulation of carbon monoxide reactivity when adsorbed at metal and oxide catalyst surfaces: Trial wave‐functions with exponential type basis and quasi‐exact three‐body correlation

Abstract

Review publications show the advantages of using quantum Monte Carlo (QMC) methods when bonding interactions are modified and consequently, where the electron correlation energy varies and needs to be evaluated accurately. This article considers a model efficient metal catalyst for reactions of carbon monoxide. The ultimate aim is to help design industrially useful catalysts, since the reaction with water produces hydrogen gas selectively, that is, a clean fuel and a sustainable energy source. To narrow the gap between the industrial process and calculation, a model of platinum/oxide is studied. It is mimicked here by copper with and without adsorbed oxygen. Periodicity as well as a validated pseudo-potential are used to limit the number of active electrons considered. A suitable code to carry out this task is CASINO. Furthermore, this code scales linearly to 100,000 processors and possesses a shared memory facility so that it is well-suited to runs on the Blugene/P. It has been in production on such computers since early in 2011. A mixed plane-wave/exponential type orbitals (ETO) basis is used for the systems studied. Plane waves are well-suited to periodic solid substrates and a linear combination of ETOs for molecules. The atomic orbitals have direct physical interpretation, i.e., Coulomb Sturmians and hydrogen-like orbitals. Their radial nodes are shown to be essential in obtaining the vitally important accurate QMC trial wave-functions. Until 2008,ETO products on different atoms were difficult to manipulate for the evaluation of two-electron integrals. Coulomb resolutions provide an excellent approximation that reduces these integrals to a sum of one-electron overlap-like integral products that each involve orbitals on at most two centers. They are thus readily evaluated. Only these integrals need to be re-evaluated to change basis functions. In this article, QMC-VMC variational optimisation is used with a quasi analytic two-electron and nucleus correlation factor. The QMC diffusion Monte Carlo methodology is applied to adsorbed carbon monoxide and some of its reactions.

Quantum and classical dynamics of reactive scattering of H2 from metal surfaces

“…A new trend is to use a novel implementation 11 of the SRP-DFT approach, 214,215 in which a weighted average of two GGA DFs is used in a semi-empirical manner in order to achieve a chemically accurate description of experiments on a specific system. New developments concern the application of embedded correlated wave function approaches 79,220,226 and of the quantum Monte-Carlo method 239,240 to H 2 -metal surface interactions.…”

Computational approaches to dissociative chemisorption on metals: towards chemical accuracy

“…The largest error is usually made in the calculation of the transition state energy, and there is some correlation between the approximate nodal error and the HOMO-LUMO gap of the reactants. 422,424 DMC calculations have been used earlier to study molecular adsorption of CO and H 2 O on Cu(100), 425 and DC of N 2 on Cu(111) 426 and of H 2 on Mg(0001). 427 Recent DMC calculations have reproduced semiempirical DC barrier heights for H 2 + Cu(111) 34 and for H 2 + Pt(111) to within 1.6 AE 1.0 and 0.9 AE 1.0 kcal mol À1 , respectively.…”

Quantum Monte Carlo with ground-state input to investigate methane reactions on supported metal film catalysts

“…The 3-center terms accounting for electron pair and nucleus correlation (each pair with a nucleus) must be present. This is already the case for molecular carbon monoxide (total energy in Hartree) from [6]:…”