Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
First-principles molecular dynamics simulations of H2O on alpha-Al2O3 (0001)
Autore:
Hass, KC; Schneider, WF; Curioni, A; Andreoni, W;
Indirizzi:
Ford Res Lab, Dearborn, MI 48121 USA Ford Res Lab Dearborn MI USA 48121Ford Res Lab, Dearborn, MI 48121 USA IBM Corp, Div Res, Zurich Res Lab, CH-8803 Ruschlikon, Switzerland IBM Corp Ruschlikon Switzerland CH-8803 CH-8803 Ruschlikon, Switzerland
Titolo Testata:
JOURNAL OF PHYSICAL CHEMISTRY B
fascicolo: 23, volume: 104, anno: 2000,
pagine: 5527 - 5540
SICI:
1520-6106(20000615)104:23<5527:FMDSOH>2.0.ZU;2-T
Fonte:
ISI
Lingua:
ENG
Soggetto:
ENERGY-LOSS SPECTROSCOPY; METAL-OXIDE SURFACES; AB-INITIO; ELECTRONIC-STRUCTURE; ALPHA-ALUMINA; GAMMA-ALUMINA; ABINITIO CHARACTERIZATION; WATER CHEMISORPTION; MGO(100) SURFACE; HYDROXYL-GROUPS;
Tipo documento:
Review
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
140
Recensione:
Indirizzi per estratti:
Indirizzo: Hass, KC Ford Res Lab, SRL MD-3028, Dearborn, MI 48121 USA Ford Res Lab SRL MD-3028 Dearborn MI USA 48121 born, MI 48121 USA
Citazione:
K.C. Hass et al., "First-principles molecular dynamics simulations of H2O on alpha-Al2O3 (0001)", J PHYS CH B, 104(23), 2000, pp. 5527-5540

Abstract

We present a more detailed account of our recently reported [Hass, K. C.; Schneider, W. F.; Curioni, A.; Andreoni, W. Science 1998, 282, 265] first-principles molecular dynamics investigation of the static and dynamical behavior of adsorbed H2O on alpha-Al2O3 (0001). Al-terminated surfaces with varying degrees of H2O coverage are modeled using large periodic supercells. Apredicted large relaxation of the clean surface agrees well with previous density functional theory calculations. Both molecular and dissociative (HO)-O-2 adsorption modes are identified, with the latter favored by similar to 10 kcal mol(-1). Complementary Al8O12 cluster results are shown to be unreliable because of their finite lateral extent. Constrained dynamical calculations of free-energy barriers indicate that the dissociation rate is veryhigh, even in the absence of defects, but differs by 3 orders of magnitudefor two equally exothermic pathways (proton transfer being more favorable across a six-membered ring than to the nearest O site). Unconstrained simulations at intermediate H2O coverages exhibit (1) spontaneous unimolecular and (2) H2O-mediated dissociation events, as well as (3) the diffusion and hydrogen bonding of physisorbed H2O and (4) an additional proton transfer reaction between adsorbed H2O and OH species, An experimentally observed decrease in H2O binding energies with coverage is explained in terms of a separation into defect-dominated, intrinsic (0001) terrace, and "hydrogen-bonding" regimes, with reasonable quantitative agreement throughout. Calculated O-H vibrational frequencies are consistent with known trends on aluminas butindicate a discrepancy between experimental observations for alpha-Al2O3 (0001) and models based on simple hydroxylation. Simulations for high H2O coverages suggest the possibility of more complicated behavior, including theinterchange of adsorbed and lattice oxygen and the etching of surface Al. A "fully"-hydroxylated alpha-Al2O3 (0001) surface in which each surface Al is replaced by three protons to give uniform OH-termination, as in aluminumhydroxides, is the most likely result of prolonged exposure. Results for this surface confirm its anticipated stability, provide a reasonable explanation of observed vibrational spectra, and reveal a complex, dynamical structure with extensive intraplanar hydrogen bonding.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 15/07/20 alle ore 04:40:55