Theoretical investigation of the interaction of CH{sub 4} with Al{sub 2} and Al{sub 3} neutral and charged clusters

Journal Article · Wed Apr 21 00:00:00 EDT 2010 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.3376174· OSTI ID:21559854

Alexandrou, E I; Bacalis, N C ^[1]; Gross, A ^[2]

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1. Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Athens 11635 (Greece)
2. Institute of Theoretical Chemistry, Ulm University, D-89069 Ulm (Germany)

We have studied the interaction of CH{sub 4} with Al{sub 2} and Al{sub 3} neutral and charged clusters in the two lowest lying spin states using density functional theory. These calculations, via extended search, are used to determine the stable positions of H and CH{sub 3} near the cluster, and the transition state to break the H-CH{sub 3} bond. In all cases, stable methyl-aluminum-hydrides are possible. The H desorption is studied by means of vibration analysis and application of transition state theory. A common observed trend is that, in breaking the H-CH{sub 3} bond, the interacting H atom is attached to the 'surface' of the clusters attracting some negative charge of {approx_equal}0.2e. The charge transfer is illustrated using the corresponding orbitals near the transition state in conjunction with the computed Mulliken population analysis. Thermal vibrations, generally, do not enhance the reaction. In all exothermic cases, the binding energy toward CH{sub 3}+HAl{sub n}{sup charge} increases with increasing charge of the original Al{sub n}{sup (q=-1,0,1)} cluster. Although Al lacks occupied d-orbitals, the small Al clusters reduce the (free methane) CH{sub 3}-H dissociation barrier except for Al{sub 3}{sup (q=-1,0)}. The relevant reactions in desorption require {approx}400-700 deg. C.

• OSTI ID: 21559854
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 15 Vol. 132; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
74 ATOMIC AND MOLECULAR PHYSICS
ALKANES
ALUMINIUM
ALUMINIUM COMPOUNDS
ALUMINIUM HYDRIDES
ATOM COLLISIONS
ATOM-MOLECULE COLLISIONS
ATOMIC CLUSTERS
ATOMS
BINDING ENERGY
CALCULATION METHODS
CHARGE EXCHANGE
CHEMICAL BONDS
COLLISIONS
DENSITY FUNCTIONAL METHOD
DESORPTION
DISSOCIATION
ELEMENTS
ENERGY
ENERGY LEVELS
EXCITED STATES
HYDRIDES
HYDROCARBONS
HYDROGEN COMPOUNDS
INTERACTIONS
ION COLLISIONS
ION-MOLECULE COLLISIONS
KINETICS
METALS
METHANE
MOLECULE COLLISIONS
ORGANIC COMPOUNDS
REACTION KINETICS
SORPTION
SURFACES
VARIATIONAL METHODS
VIBRATIONAL STATES