Computer Simulation of .gamma.-Al2O3 Microcrystal

Álvarez, Luis Javier; León, Luis E.; Sanz, Javier Fernández; Capitán, M. J.; Odriozola, J.A.

doi:10.1021/j100051a011

Cited by 55 publications

(30 citation statements)

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“…The O͑Al 2 O 3 ͒ and Al͑Al 2 O 3 ͒ charges were taken from the local-orbital Hartree-Fock calculations of Ref. 13, which yield values near the midpoints of the relatively wide ranges of atomic charges found in published calculations [12][13][14]17,46,47 for bulk and surface ␣-Al 2 O 3 . To avoid an unrealistically large electrostatic attraction between the H of a water molecule and surface O, we include pairwise Lennard-Jones interactions between all four combinations of water and surface atoms.…”

Section: Water-alumina Interactionsmentioning

confidence: 99%

Simulations of hydrocarbon adsorption and subsequent water penetration on an aluminum oxide surface

Claire

Hass

Schneider

et al. 1997

The Journal of Chemical Physics

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International audienceStatic and dynamic equilibrium properties of butane octane, and dodecane films adsorbed on α-Al2O3(0001) at a variety of coverages and temperatures, and the subsequent penetration of such films by 30 molecule water clusters are examined using classical molecular dynamics. Model potential functions are constructed from existing alkane united atom and "simple point charge" model water parameters, experimental alkane desorption energies and other available theoretical information. The adsorbed films exhibit a distinct layering parallel to the surface, and a pronounced densification, reduction in gauche defects and orientational ordering within the innermost layer. Strong surface corrugation allows molecules to rotate relatively freely about their long axes at intermediate temperatures and assists them in orienting their zig-zag planes perpendicular to the surface at lower temperatures. Only butane molecules show any tendency to tilt their long axes out of the first layer toward the second. (H2O)30 clusters are attracted toward the alumina surface and easily penetrate most of the adsorbed alkane films, either by displacing alkane molecules to more distant layers or causing them to pack more closely within existing layers. The molecules in the clusters tend to remain connected during penetration. Kinetic barriers to penetration become increasingly significant for higher alkane coverages, lower temperatures, and longer chains

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Section: Water-alumina Interactionsmentioning

confidence: 99%

Simulations of hydrocarbon adsorption and subsequent water penetration on an aluminum oxide surface

Claire

Hass

Schneider

et al. 1997

The Journal of Chemical Physics

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“…A pairwise interaction potential was used in the simulation. 1,2 The large size of this system permits one to study the relationship between the bulk and the surface structures. The ''theoretical particle'' has an edge of 5.5 nm.…”

Section: Introductionmentioning

confidence: 99%

Modeling Lewis acidity of transition aluminas by numerical simulations

Álvarez

Blumenfeld

Fripiat

1998

The Journal of Chemical Physics

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The application of infrared spectroscopy to probe the surface morphology of alumina-supported palladium catalysts A density functional model for tuning the charge transfer between a transition metal electrode and a chemisorbed molecule via the electrode potentialThe bulk and surface features of an alumina particle obtained by molecular-dynamics simulation are used to support the experimental distribution of aluminums with respect to their coordination number obtained by NMR ͑nuclear magnetic resonance͒. This information was obtained by using results of various editing procedures of the 27 Al nuclear magnetic resonance, such as the classical one-pulse ͑1P͒ magic angle spinning, the cross polarization ͑CP͒ from the protons of chemisorbed ammonia and the 1P or CP rotational echo double resonance ͑REDOR͒. Because the REDOR technique revealed that the acid Lewis sites are constituted by pairs of four or fivefold coordinated aluminum atoms about 3 Å apart, these pairs were counted in the simulated particle. The agreement with experimental surface density of Lewis sites is satisfactory.

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“…Extensive simulation studies of the structure and dynamics of ␥-alumina have been reported and the interpretation of its structure has been approached correlating simulation results with different experimental techniques. 3 Recently a report of the experimental determination of the structure of liquid aluminum oxide has been published. 1 In order to complement this experiment, in this work we report the results of molecular-dynamics ͑MD͒ simulations of liquid aluminum oxide, and discuss a model to describe its structure.…”

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confidence: 99%

Molecular-dynamics simulations of liquid aluminum oxide

et al. 1998

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The total and partial radial distribution functions g(r) and the corresponding structure factors S(q) were calculated based on molecular-dynamics simulations in the microcanonical ensemble of liquid aluminum oxide. The simulations were performed in the temperature range 2300-3000 K in order to explore the temperature dependence of the structure, finding that the liquid structure is invariant as a function of temperature. With the aid of the partial radial distribution functions, it is possible to reinterpret the experimental data leading to a new assignment of peaks which differs from the one reported in a previously published work by Ansell et al. ͓Phys. Rev. Lett. 78, 464 ͑1997͔͒. The structural model for liquid aluminum oxide obtained from our simulations is essentially the same as that reported in the experimental work. ͓S0163-1829͑98͒01530-6͔

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Computer Simulation of .gamma.-Al2O3 Microcrystal

Cited by 55 publications

References 0 publications

Simulations of hydrocarbon adsorption and subsequent water penetration on an aluminum oxide surface

Simulations of hydrocarbon adsorption and subsequent water penetration on an aluminum oxide surface

Modeling Lewis acidity of transition aluminas by numerical simulations

Molecular-dynamics simulations of liquid aluminum oxide

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