An electronic structure study of H[sub 2] and CH[sub 4] interactions with MgO and Li-doped MgO clusters

Journal Article · Fri Oct 15 04:00:00 EDT 1993 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.465899· OSTI ID:6219563

Anchell, J L; Morokuma, K ^[1]; Hess, A C ^[2]

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1. Institute for Molecular Science, Myodaiji, Okazaki 444 (Japan)
2. Pacific Northwest Laboratory, MSIN K1-90, Richland, Washington 99352 (United States)

An [ital ab] [ital initio] study is presented concerning the chemisorption of hydrogen on a model of the (100) surface of MgO and Li-doped MgO. The local surface environment was modeled employing cubic and tetragonal clusters composed of 8 and 12 atoms, respectively. The lattice constant for the clusters was fixed at the experimentally determined value for bulk MgO and the geometry of the adsorbate was optimized at the unrestricted Hartree--Fock (UHF) level of theory. Correlation energy was treated at the second-order unrestricted Moller--Plesset (UMP2) level at the UHF optimized geometry. It was found that H[sub 2] undergoes heterolytic dissociation at neighboring three-coordinated Mg and O sites (denoted Mg[sub 3[ital c]] and O[sub 3[ital c]]) in MgO with activation energies of 4.2 and 2.4 kcal/mol at the UHF and UMP2 levels, respectively. Li-doped MgO did not support heterolytic dissociation at neighboring Mg and O sites. Instead H[sub 2] was found to dissociate homolytically without barrier at two O[sub 3[ital c]] sites and to undergo hydrogen atom abstraction at O[sub 3[ital c]] and O[sub 4[ital c]] sites. At the UHF/UMP2 level, it was found that at O[sub 3[ital c]] sites, abstraction occurs with a 17.9/3.0 kcal/mol barrier, and at O[sub 4[ital c]] sites, abstraction occurs with a 15.7/0.6 kcal/mol activation energy.

• DOE Contract Number: AC06-76RL01830
• OSTI ID: 6219563
• Journal Information: Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 99:8; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
360606 -- Other Materials-- Physical Properties-- (1992-)
ACTIVATION ENERGY
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
ALKANES
ALLOYS
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISORPTION
ELECTRONIC STRUCTURE
ELEMENTS
ENERGY
GEOMETRY
HYDROCARBONS
HYDROGEN
LATTICE PARAMETERS
LITHIUM ADDITIONS
LITHIUM ALLOYS
LITHIUM COMPOUNDS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MATHEMATICS
METHANE
MOLECULAR CLUSTERS
NONMETALS
OPTIMIZATION
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
SEPARATION PROCESSES
SORPTION
SORPTIVE PROPERTIES
SURFACE PROPERTIES