Amorphous materials represent a large and important emerging area of material's science. Amorphous oxides are key technological oxides in applications such as a gate dielectric in Complementary metal-oxide semiconductor devices and in Silicon-Oxide-NitrideOxide-Silicon and TANOS (TaN-Al 2 O 3 -Si 3 N 4 -SiO 2 -Silicon) flash memories. These technologies are required for the high packing density of today's integrated circuits. Therefore the investigation of defect states in these structures is crucial. In this work we present X-ray synchrotron measurements, with an energy resolution which is about 5-10 times higher than is attainable with standard spectrometers, of amorphous alumina. We demonstrate that our experimental results are in agreement with calculated spectra of amorphous alumina which we have generated by stochastic quenching. This first principles method, which we have recently developed, is found to be superior to molecular dynamics in simulating the rapid gas to solid transition that takes place as this material is deposited for thin film applications. We detect and analyze in detail states in the band gap that originate from oxygen pairs. Similar states were previously found in amorphous alumina by other spectroscopic methods and were assigned to oxygen vacancies claimed to act mutually as electron and hole traps. The oxygen pairs which we probe in this work act as hole traps only and will influence the information retention in electronic devices. In amorphous silica oxygen pairs have already been found, thus they may be a feature which is characteristic also of other amorphous metal oxides.stochastic quench | X-ray absorption spectroscopy | ab initio | coating D espite early attempts to describe the fundamental electronic properties of noncrystalline semiconductors (1-5), experimental and theoretical knowledge of localized states in the gap of amorphous semiconductors and insulators is still limited. General features of the electronic structure of amorphous semiconductors are quite well known, such as the broad distribution of coordinations and the lack of long range order that induces valence and conduction band tails in the band gap (6). However, the origin of these states is less explored experimentally (7,8) and theoretical investigations are mainly limited to the crystalline polymorphs (9-11). Amorphous Alumina (am-Al 2 O 3 ) is currently one of the key technological amorphous materials, where one promising application of am-Al 2 O 3 is as a high-k dielectric in transistors (12). The use of am-Al 2 O 3 in TANOS (TaN-Al 2 O 3 -Si 3 N 4 -SiO 2 -Silicon) flash memories, which are currently investigated for gigabite and terabite scale flash memories, puts even higher demands on alumina as a current-blocking high-k dielectric.From optical absorption and photoluminescence, states related to F-centers (9, 10) and impurities have been identified in the band gap of am-Al 2 O 3 down to 3.18 and 3.25 eV relative to the valence band edge (13,14). In another study, electronbeam induced states in the am-Al ...

We investigate the distribution of local minima in the potential-energy landscape of metals. The density of energy minima is calculated for Na by using a pair-potential method to quench from stochastic configurations for system sizes ranging from 1 to 4000 atoms. We find a minimum system size, approximately 150 atoms, above which the density of energy minima is dominated by one sharp peak. As the system size is increased, the peak position converges to an asymptotic value and its width converges to zero. The findings of the pairpotential method for Na are confirmed by first-principles calculations of amorphous Al and V. Finally we present an example in which our results are applied to the complex bulk metallic glass Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 ͑Vitreloy 105͒. The calculated density and bulk modulus of the Vitreloy are in good agreement with experiments. The analysis presented here shows that the thermodynamic limit is better described by one large supercell calculation than by an average over many smaller supercell calculations. We argue that the minimum cell size that is needed to accurately perform such a large supercell calculation for metallic glasses is about 150 atoms.

It is possible in principle to probe the many-atom potential surface using density functional theory (DFT). This will allow us to apply DFT to the Hamiltonian formulation of atomic motion in monatomic liquids by Wallace [Phys. Rev. E 56, 4179 (1997)]. For a monatomic system, analysis of the potential surface is facilitated by the random and symmetric classification of potential-energy valleys. Since the random valleys are numerically dominant and uniform in their macroscopic potential properties, only a few quenches are necessary to establish these properties. Here we describe an efficient technique for doing this. Quenches are done from easily generated "stochastic" configurations, in which the nuclei are distributed uniformly within a constraint limiting the closeness of approach. For metallic Na with atomic pair potential interactions, it is shown that quenches from stochastic configurations and quenches from equilibrium liquid molecular dynamics configurations produce statistically identical distributions of the structural potential energy. Again for metallic Na, it is shown that DFT quenches from stochastic configurations provide the parameters which calibrate the Hamiltonian. A statistical mechanical analysis shows how the underlying potential properties can be extracted from the distributions found in quenches from stochastic configurations.

In order to test the vibration-transit (V-T) theory of liquid dynamics, ab initio density functional theory (DFT) calculations of thermodynamic properties of Na and Cu are performed and compared with experimental data. The calculations are done for the crystal at T = 0 and Tm, and for the liquid at Tm. The key theoretical quantities for crystal and liquid are the structural potential and the dynamical matrix, both as functions of volume. The theoretical equations are presented, as well as details of the DFT computations. The properties compared with experiment are the equilibrium volume, the isothermal bulk modulus, the internal energy and the entropy. The agreement of theory with experiment is uniformly good. Our primary conclusion is that the application of DFT to V-T theory is feasible, and the resulting liquid calculations achieve the same level of accuracy as does ab initio lattice dynamics for crystals. Moreover, given the well established reliability of DFT, the present results provide a significant confirmation of V-T theory itself.

Erratum: "Density depletion profile and solvation free energy of a colloidal particle in a polymer solution" [J.The gas-liquid density profile and surface tension are calculated for a fluid possessing hard sphere repulsion, van der Waals-like dispersion, and sticky-spot attraction. The sticky spot allows monomers to dimerize and the consequences of which are investigated. Association is treated with Wertheim's thermodynamic perturbation theory and the direct correlation functions are derived by means of the Ornstein-Zernike equations for associating systems. The primary effect of association is to shift the critical temperatures and densities from those of a nonassociating fluid. While there are small, nonmonotonic shifts in the correlation length and surface tension, accompanied by an interface composition change, these effects on the density profile seem to be subsumed in the use of the proper T/T c .