Theory and experiments on the structure of 7Å alumina films grown on Ni3Al

Qin, F.; Magtoto, N.P.; Kelber, J. A.; Jennison, D. R.

doi:10.1016/j.molcata.2004.09.082

Cited by 9 publications

(5 citation statements)

References 43 publications

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“…In general, longer oxidation times yielded thicker films, while longer annealing times in UHV resulted in gradual decreases in average film thickness, as observed by AES. Ordered oxide films 7 Å thick were observed on Ni 3 Al(1 1 0) with LEED and STM images (not shown) in good agreement with published results [8,9,25]. Thicker films yielded a sharp, similar LEED pattern, but STM imaging proved extremely difficult.…”

Section: Experimental Methodssupporting

confidence: 88%

“…3) were indicative of Al 2 O 3 . LEED images (not shown) observed prior to H 2 O exposure were in good agreement with those previously published for a 7 Å film [9,25] and a chemisorbed O monolayer [17], with lines of diffuse scattering perpendicular to the (1 1 0) direction. STM imaging proved very difficult on this surface.…”

Section: Characterization Of Oxide Films Formed In Uhvsupporting

confidence: 88%

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Reactivities of ultrathin alumina films exposed to intermediate pressures of H2O: Substrate-mediated mechanism for growth and loss of surface order

et al. 2007

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Section: Experimental Methodssupporting

confidence: 88%

Section: Characterization Of Oxide Films Formed In Uhvsupporting

confidence: 88%

Reactivities of ultrathin alumina films exposed to intermediate pressures of H2O: Substrate-mediated mechanism for growth and loss of surface order

et al. 2007

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“…One of the most important water–mineral interfaces is the aluminum-oxide–water interface, otherwise known as an alumina–water interface. Because alumina has a low dissolution rate, stable surface structure, , and can form stable thin films, it is important in catalysis ,, and microelectronics. , In addition, due to its ubiquity in the environment, the ability of the alumina–water interface to adsorb organic and inorganic compounds is important for health and environmental chemistry …”

Section: Introductionmentioning

confidence: 99%

Relating Interfacial Order to Sum Frequency Generation with Ab Initio Simulations of the Aqueous Al₂O₃(0001) and (112̅0) Interfaces

et al. 2018

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We use density functional theory molecular dynamics simulations to investigate the structure, dynamics, and vibrational sum frequency generation (vSFG) spectra at the Al 2 O 3 (0001)−H 2 O and Al 2 O 3 (112̅ 0)−H 2 O interfaces. We find that the differences in the vSFG spectra between the two interfaces can be explained by significantly weaker surface−water interactions at the (0001) vs (112̅ 0) interface. The weaker interactions at the (0001) surface are caused by the flat surface plane and high density of OH groups, leading to a decoupling of the vibrational modes of the surface OH groups and H 2 O molecules. The (0001) vSFG spectrum thus displays two well-separated peaks at the near-neutral pH, in contrast to the vSFG spectrum of the corrugated (112̅ 0) interface, which has stronger surface−water interactions and thereby a narrower band in the vSFG spectrum with closely spaced peaks. By simulating the interfaces with both the Perdew−Burke−Ernzerhof (PBE)−Tkatchenko−Scheffler and revised PBE (RPBE) functionals, we find that a proper description of the separation of surface and solution H-bond modes is essential to obtain accurate SFG spectra. The RPBE functional was unable to accurately model the H-bonds of H 2 O and surface aluminols simultaneously. Finally, we use the H-bond lifetimes and the tetrahedral order parameter for H 2 O to conclude that water at the (0001) surface is more ordered than at the (112̅ 0) surface, in contrast to prior interpretations of of X-ray reflectivity and vSFG experiments, highlighting the importance of atomistic models of the H-bond structure and dynamics of the water−oxide interfaces.

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“…7,8 Ultrathin alumina films on intermetallic alloys are widely studied as nanotemplates to support model catalysts, but the structural details of the oxide/alloy interfaces remain difficult to resolve and control. [9][10][11][12][13][14][15][16] Recent combined experimental and theoretical investigations on NiAl(110) 13,15 and Ni 3 Al(111) 16 concluded that the films (two O layer thick and O-terminated) have an overall stoichiometric Al/O ratio (1:1.3) higher than that of Al 2 O 3 (1:1.5), and they are largely distorted with respect to bulk alumina structures. An unmodified alloy surface at the interface with the oxide was proposed, assuming perfect rehomogenization of the alloy surface after oxidation and thereby disregarding the possible structural modifications induced by vacancy injection.…”

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confidence: 99%

Atomistic Modeling of Voiding Mechanisms at Oxide/Alloy Interfaces

et al. 2009

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For the first time, voiding mechanisms resulting from the condensation of atomic vacancies injected at oxide/alloy interfaces by the growth of oxide layers have been studied by means of periodic density functional theory (DFT) calculations. Several interfaces were built by superimposing ultrathin films of alumina on the γ-TiAl(111) surface, and their relative stabilities were compared by calculating the interface energy variation. The formation energy of single Ti or Al vacancies and clustered and dispersed ensembles of 2Ti + 1Al or 2Al + 1Ti vacancies injected into the alloy were calculated. The results show that it is easier to inject the vacancies into the oxide/alloy interface than into the bare alloy surface and into the bulk alloy. The injected vacancies, trapped at the oxide/alloy interface, condense in the topmost plane of the alloy to form 2D clusters. The minimization of the coordination number of the vacancies with metal atoms of the alloy and O atoms of the overlaying oxide favors vacancy condensation and interfacial voiding. The data are relevant for a detailed understanding of the adherence and breakdown of protective oxide films and the lifetime of metallic materials.

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Theory and experiments on the structure of 7Å alumina films grown on Ni3Al

Cited by 9 publications

References 43 publications

Reactivities of ultrathin alumina films exposed to intermediate pressures of H2O: Substrate-mediated mechanism for growth and loss of surface order

Reactivities of ultrathin alumina films exposed to intermediate pressures of H2O: Substrate-mediated mechanism for growth and loss of surface order

Relating Interfacial Order to Sum Frequency Generation with Ab Initio Simulations of the Aqueous Al₂O₃(0001) and (112̅0) Interfaces

Atomistic Modeling of Voiding Mechanisms at Oxide/Alloy Interfaces

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Theory and experiments on the structure of 7Å alumina films grown on Ni3Al

Cited by 9 publications

References 43 publications

Reactivities of ultrathin alumina films exposed to intermediate pressures of H2O: Substrate-mediated mechanism for growth and loss of surface order

Reactivities of ultrathin alumina films exposed to intermediate pressures of H2O: Substrate-mediated mechanism for growth and loss of surface order

Relating Interfacial Order to Sum Frequency Generation with Ab Initio Simulations of the Aqueous Al2O3(0001) and (112̅0) Interfaces

Atomistic Modeling of Voiding Mechanisms at Oxide/Alloy Interfaces

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Relating Interfacial Order to Sum Frequency Generation with Ab Initio Simulations of the Aqueous Al₂O₃(0001) and (112̅0) Interfaces