{ital Ab initio} and semiempirical studies of the adsorption and dissociation of water on pure, defective, and doped MgO (001) surfaces

Journal Article · Tue Sep 01 04:00:00 EDT 1998 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.476964· OSTI ID:641516

Almeida, A L; Martins, J B; Taft, C A ^[1]; Longo, E ^[2]; Lester, Jr, W A ^[3]

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1. Centro Brasileiro de Pesquisas Fisicas, Departamento de Materia Condensada e Fisica Estatistica, Rua Dr. Xavier Sigaud 150, Rio de Janeiro RJ, Cep 22290-180 (Brazil)
2. Universidade Federal de Sao Carlos, Departamento de Quimica, CP 676, Sao Carlos, S.P., CEP 13565-905 (Brazil)
3. Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720-1460 (United States)

{ital Ab initio} and semiempirical calculations of large cluster models have been performed in order to study water adsorption and dissociation on pure, defective (vacancies) and doped (Li, Na, K, Ca, Fe) MgO (001) surfaces. The geometries of the adsorbed and dissociated molecules have been optimized preparatory to analysis of binding energies, stretching frequencies, charge transfers, preferential sites of interaction, and bond distances. We have used Mulliken, natural bond order, and electrostatic-derived atomic and overlap populations to analyze charge distributions in the clusters. We have also investigated transition structures, activation energies, energy gaps, HOMO, density of states, SCF orbital energies as well as the acid{endash}base properties of our cluster model. Numerical results are compared, where possible, with experiment, interpreted in the framework of various analytical models, and correlated with site coordination numbers, corner and edge site preferential locations, and direction of charge transfer. A thorough charge analysis indicates substantial charge redistribution in the magnesium oxide crystal as a result of water adsorption and dissociation in pure, defective, and doped MgO crystals. The introduction of heavier impurities and vacancies could produce substantial changes in the physical and chemical properties of the catalyst and increase the binding and dissociation energies. Some of the largest changes originate from the introduction of vacancies. Two and three-dimensional potential energy surfaces are used to investigate activation energies of hydroxylation on the MgO surface. Stretching frequencies are correlated with magnesium and oxygen coordination numbers. {copyright} {ital 1998 American Institute of Physics.}

• OSTI ID: 641516
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 9 Vol. 109; ISSN 0021-9606; ISSN JCPSA6
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ADSORBENTS
ADSORPTION
BINDING ENERGY
CHARGE EXCHANGE
DISSOCIATION
DOPED MATERIALS
MAGNESIUM OXIDES
SUBSTRATES
WATER