A ReaxFF potential for Al - ZnO systems

A reactive field force (ReaxFF) potential has been created in order to model the structural effects of low percentage dopant aluminium in a zinc oxide system. The potential’s parameters were fitted to configurations computed with Density Functional Theory (DFT): cohesive energies, binding energies and forces were all considered for bulk crystals, surface structures and ZnAl alloys. As a first application of the model, the energetic deposition (0.1 - 40 eV) of an aluminium atom onto the polar surface of a ZnO (000 ̄1) is considered. For low energies the Al atom attaches to two preferred sites on the surface but as the energy increases above ≈ 15 eV subplantation is preferred at near normal incidence, with high diffusion barriers between stable sites. At these energies, reflection of the Al atom occurs at incident angles above ≈ 55◦.

In silico search for planar hexacoordinate Silicon atom: A kinetically viable species

In silico search for planar hexacoordinate silicon center has been initiated by global minimum screening with density functional theory and energy refinement using coupled cluster theory. The search resulted in a local minimum of SiAl3Mg3H2+ structure which contains a planar hexacoordinate silicon center (phSi). The phSi structure is 5.8 kcal/mol higher in energy than the global minimum. However, kinetic studies reveal that the local minimum structure has enough stability to be detected experimentally. Born-Oppenheimer molecular dynamics (BOMD) simulations reveal that the phSi structure can be maintained up to 400 K. The formation of multiple bonds between the central silicon atom and framework aluminium atom is the key stabilizing factor for the planar structure.

The crystal structure of the decaaluminum alkoxide cluster Al10O4(OH)8 L 14 (L = 1,1,1,3,3,3-hexafluoropropan-2-olate)

In the title centrosymmetric cluster compound, hexakis(μ2-1,1,1,3,3,3-hexafluoropropan-2-olato)octakis(1,1,1,3,3,3-hexafluoropropan-2-olato)octa-μ2-hydroxido-di-μ4-oxido-di-μ3-oxido-decaaluminium, [Al10(C3HF6O)14(OH)8O4] (C42H22Al10F84O26), there is a central μ4-OAl4 moiety, which has six edges of which three contain μ(O)-1,1,1,3,3,3-hexafluoropropan-2-olate (L) ligands and two contain μ-OH groups each bridging two Al atoms along an edge. The sixth edge is occupied by a group containing a fifth aluminium atom [bis-μ(OH)-, μ3(O)—AlL]. This last μ3(O) group generates a centrosymmetric Al2O2 dimer, thus the μ3(O) atom is linked to two Al atoms in the asymmetric unit as well as a third Al atom through a center of inversion. Three of the hexafluoropropyl groups of the C3HF6O− ligands are disordered and each was refined with two conformations with occupancies of 0.770 (3)/0.230 (3), 0.772 (3)/0.228 (3) and 0.775 (3)/0.225 (3). The five unique Al centers have coordination numbers varying from four to six with bond angles that show considerable distortions from regular geometry: for the four-coordinate atom, τ4′ = 0.886, while three Al atoms are five-coordinate (τ5 values = 0.098, 1.028, and 0.338) and one is distorted six-coordinate with O—Al—O bond angles ranging from 74.22 (9) to 171.59 (12)°. The geometry about the central O atom in the OAl4 block is significantly distorted tetrahedral (τ4′ = 0.630) with Al—O—Al angles ranging from 95.50 (9) to 147.74 (13)°. The extended structure features numerous O—H...O, O—H...F, C—H...O and C—H...F hydrogen bonds and short F...F contacts.

Dissecting the Effects of Water Guest Adsorption and Framework Breathing on the AlO4(OH)2 Centers of Metal-Organic Framework MIL-53 (Al) by Solid State NMR and Structural Analysis

The relationship between the adsorption of water on MIL-53 (Al) MOF, the structural phase of MIL-53 (Al), and quadrupole coupling constant of 27Al framework aluminium atom (QCC) of the MOF...

Tris(6-tert-butyl-4-methylpyridazine-3-thiolato-κ2N,S)aluminium

The title complex, [Al(C9H13N2S)3], is composed of an aluminium atom coordinated by three bidentate thiopyridazine ligands in an octahedral environment. It has approximateC3symmetry, with Al—N distances in the range 1.9732 (17)–1.9794 (17) Å and three Al—S distances in the range 2.3961 (8)–2.4354 (8) Å. In the crystal, there are no significant intermolecular interactions present.

Synthesis, characterization and crystal structure of a 2-(diethylaminomethyl)indole ligated dimethylaluminium complex

The title compound, [Al(CH3)2(C13H17N2)] (systematic name; {2-[(diethylamino)methyl]indol-1-yl-κ2N,N′}dimethylaluminium), was prepared by methane elimination from the reaction of 2-(diethylaminomethyl)indole and trimethylaluminium. The complex crystallizes readily from a concentrated toluene solution in high yield. The asymmetric unit contains two crystallographically independent molecules. Each molecule has a four-coordinate aluminium atom that has pseudo-tetrahedral geometry. C—H...π interactions link the independent molecules into chains extending along theb-axis direction.

Studying on Rare Earth Aluminizing Process of GH4169 Superalloy

The aluminizing process by solid powder on the surface of GH4169 superalloy with different Y2O3content and different aluminizing temperature was investigated in this paper. The results show that the crystalline phase of aluminized coating is composed of AlNi, FeNi and AlNi3, and the phase of AlNi reaches 78.1%, which indicates that aluminium atom has infiltrated into the alloy surface. Y2O3can greatly improve compactness of the aluminized coating, increase thickness, surface micro-hardness and high temperature oxidation resistance of the aluminized coating. The thickness of the coating increases with the increase of temperature, but the microstructure of the aluminized samples cannot obviously divided into aluminized layer, transition layer and matrix when the aluminizing temperature is too high (980°C) or too low (920°C), and even the aluminized coating is porous and coarse at 980°C. The high temperature oxidation resistance of all the aluminized samples is improved compared to without aluminized samples. According to the microstructure, thickness, surface micro-hardness and high temperature oxidation resistance of aluminized coating, the optimal aluminizing process is 950°C×7h with 4%Y2O3.