Search

Recent experiments have demonstrated that plastic strains in nanocrystalline aluminum and gold films with grain sizes on the order of 50 nm are partially recoverable. To reveal the mechanisms behind such strain recovery, we perform large scale molecular dynamics simulations of plastic deformation in nanocrystalline aluminum with mean grain sizes of 10, 20, and 30 nm. Our results indicate that the inhomogeneous deformation in a polycrystalline environment results in significant residual stresses in the nanocrystals. Upon unloading, these internal residual stresses cause strain recovery via competitive deformation mechanisms including dislocation reverse motion/annihilation and grain-boundary sliding/diffusion. By tracking the evolution of each individual deformation mechanism during strain recovery, we quantify the fractional contributions by grain-boundary and dislocation deformation mechanisms to the overall recovered strain. Our analysis shows that, even under strain rates as high as those in molecular dynamics simulations, grain-boundary-mediated processes play important roles in the deformation of nanocrystalline aluminum. grain-boundary diffusion | grain-boundary sliding | molecular dynamics simulation

Several experimental and computational studies are conducted to determine the forward current density ([J.sub.F])-forward voltage ([V.sub.F]) characteristics of 4H-silicon junction barrier Schottky (JBS) diodes. These characteristics are shown to be highly affected by the lateral spreading of the implanted aluminum ions and implantation-induced defects.

Aluminum ion doping to the Ni fully silicided/HfSiON gate stack is used to demonstrate a simplified method of effective work function control for n-channel metal-oxide-semiconductor. The formation of interfacial [Al.sub.2] [O.sub.3] layer at the Ni-FUSI/Si[O.sub.2] interface gives rise to opposite effective work function that has little influence on the effective work function value on the Ni fully silicided/HfSiON interface.

Good linear correlations between GIAO-MP2 calculated (super 11)B NMR chemical shifts of boronium-onium cations and (super 13)C NMR chemical shift of the corresponding isoelectronic carbonium-onium dications as well as between (super 27)Al NMR chemical shifts of the alonium-onium cations and the (super 29) Si NMR chemical shifts of the corresponding isoelectronic siliconium-onium dications are observed.

The results of a theoretical study of MnNn (M =Al, Ga, and In; n = 4,5,6) neutral and anionic clusters are reported that focus on the changes in structural and electronic properties upon the addition of an electron to the corresponding neutral clusters. The atomic charge analysis showed that the extra electron is localized on the metal atoms, irrespective of the lowest energy structural configurations of these clusters.

The nanoenergetic materials consisting of aluminum nanoparticle (50 - 200 nm) aggregates termed ALEX plus nitrocellulose (NC) oxidizer are studied by ultrafast spectroscopy following 100 ps laser flash-heating. The nanosecond-duration burst of light accompanying ignition triggered by vaporizing ALEX consists of a continuum peaked near 500 nm plus features associated with electronically excited Al atoms and hot excited AlO.

A combination of W-band (super 1)H ENDOR and X-band HYSCORE spectroscopies has provided direct evidence of the coordination environment of Cu(super 2+) exchanged in zeolite Y. W-band (super 1)H ENDOR is used to probe the water ligands, whereas X-band hyperfine sublevel correlation (HYSCORE) spectroscopic measurements were employed to detect (super 27)Al hyperfine couplings.

The product energy and angular momentum distribution for dissociation of the Al(sub 6) and Al(sub 13) clusters are presented which are compared with the predictions of statistical theories. The report stated that EngelRing model for deducing the cluster dissociation energy from the measured does not give accurate results for Al(sub 6) and Al(sub 3) dissociations.

Nitrogen-incorporated SAPO-11 molecular sieves are synthesized by a secondary synthesis technique at low nitridation temperature (400 degree C) with a starting material of SAPO-11 zeolite doped with two wt % Ru. It was found that nitrogen-containing species had incorporated into framework of SAPO-11 zeolite, in which some N atoms directly bonded to Al and P atoms and formed AlN4, AlN2O2, and PN4 groups.

The gas electron diffraction (GED) method along with quantum chemical calculations were used to determine the molecular structures of chloro(phthalocyaninato)aluminum(III) (ClPcAl) and chloro(phthalocyaninato)-gallium(III) (ClPcGa). The results from calculations showed all the molecules to have [C.sub.4v] symmetry with the metal atom above the plane defined by the four inner cavity N atoms and an almost planar macrocycle.

A series of alumino-carbon clusters, [C.sub.n][Al.sub.m](n=2-3, m=2-8) are computationally investigated at MP2 level of theory with correlation consistent basis sets augmented on carbon. Studied carbon-aluminum clusters exhibit a significant stability toward ionization and moderate electron attachment.

Density functional theory method is used to study the binding of cytosine to aluminum(Al), copper(Cu), and gold(Ag). In [(Al-cytosine).super. -1] the bonding shows electrostatic and covalent interactions and the negative atomic charge of Cu and Ag produce nonconventional hydrogen bonds in [(Cu-cytosine).super. -1] and [(Ag-cytosine).super.-1].

The thermodynamic properties of Al are calculated for two nonpairwise-additive potentials by using Monte Carlo simulations. The results have shown that the melting point for the embedded-atom model is higher than the experimental value and the embedded-atom (EAM) potential has yielded improved binding energies for smaller clusters, a small fraction of aggregates in the saturated vapor phase, and hence an accurate heat of vaporization and boiling point.

Mass spectroscopy, anion photoelectron spectroscopy, photoionization spectroscopy, and theoretical calculations were employed to investigate the geometric and electronic structures of aluminum binary clusters, [Al.sub.n]X (X = Si and P). Experimental and theoretical results reveal that Al12Si possesses a high ionization energy and low electron affinity and Al12P possesses a low ionization energy, both with the icosahedral structure having a central Si or P atom, revealing that Al12Si and Al12P exhibit rare-gas-like and alkali superatoms, respectively.

The protonation mechanisms of olefins in H-ZSM-5 at the DFT level of theory with representative cluster sizes to gain insights into the relative stability of alkoxy species are studied. The barriers and mechanism for their formation from olefins as well as the interaction of saturated paraffin molecules with Bronsted acid sites are also investigated.

Al and Ti into the framework of ordered mesoporpous silica materials in strong acidic media in the presence of triblock polymer template, resulting in the formation of mesoporous aluminosilicate (MAS-7) and mesoporous titanosilicate (MTS-9) is introduced. The results of the catalytic tests show that MAS-7 gives higher catalytic activity in the crackings of cumene and 1,3,5-triisopropylbenzene than Al-SBA-15, and MTS-9 provides higher catalytic activity in phenol hydroxylation by H2O2 than Ti-SBA-15.

A set of first principles calculations is conducted in order to determine the interaction of a (pi) bonded organic molecule with a simple s-p metal surface. The findings indicate that the binding between a (pi) and the (pi) orbitals of a simple metal atom cannot be extended to describe the binding with a p band of solid.