Revisiting the Al/Al₂O₃ interface: coherent interfaces and misfit accommodation.

We study the coherent and semi-coherent Al/α-Al2O3 interfaces using molecular dynamics simulations with a mixed, metallic-ionic atomistic model. For the coherent interfaces, both Al-terminated and O-terminated nonstoichiometric interfaces have been studied and their relative stability has been established. To understand the misfit accommodation at the semi-coherent interface, a 1-dimensional (1D) misfit dislocation model and a 2-dimensional (2D) dislocation network model have been studied.

Atomistic Modeling of the Negative Thermal Expansion in δ- Plutonium Based on the Two-State Description.

The δ phase of plutonium with the fcc structure exhibits an unusual negative thermal expansion (NTE) over its narrow temperature range of stability, 593-736 K. An accurate description of the anomalous high-temperature volume effect of plutonium goes beyond the current capability of electronic-structure calculations. We propose an atomistic scheme to model the thermodynamic properties of δ-Pu based on the two-state model of Weiss for the Invar alloys, inspired by the simple free-energy analysis previously conducted by Lawson et al.

Atomistic modeling of thermodynamic equilibrium and polymorphism of iron.

We develop two new modified embedded-atom method (MEAM) potentials for elemental iron, intended to reproduce the experimental phase stability with respect to both temperature and pressure. These simple interatomic potentials are fitted to a wide variety of material properties of bcc iron in close agreement with experiments. Numerous defect properties of bcc iron and bulk properties of the two close-packed structures calculated with these models are in reasonable agreement with the available first-principles calculations and experiments.

Quantum Mechanical Origins of the Iczkowski-Margrave Model of Chemical Potential.

Charge flow in materials at the atomistic level is controlled through chemical potential equalization among its constituents. Consequently employing this concept in a simulation requires some model of chemical potential. Current atomistic models of chemical potential, such as the Iczkowski-Margrave (IM) model, are built largely on heuristic arguments and depend linearly on the net charge of each constituent.

Energy dependence on fractional charge for strongly interacting subsystems.

The energies of a pair of strongly interacting subsystems with arbitrary noninteger charges are examined from closed- and open-system perspectives. An ensemble representation of the charge dependence is derived, valid at all interaction strengths. Transforming from resonance-state ionicity to ensemble charge dependence imposes physical constraints on the occupation numbers in the strong-interaction limit.

An empirical charge transfer potential with correct dissociation limits.

The empirical valence bond (EVB) method [J. Chem. Phys.