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Author(s): Luis A. Zepeda-Ruiz [1]; Alexander Stukowski [2]; Tomas Oppelstrup [1]; Vasily V. Bulatov (corresponding author) [1] Ordinarily, the strength and plasticity properties of a metal are defined by dislocations--line [...]

Several molecular dynamics (MD) simulations are employed to explain the characterization of sputtering products obtained during the graphite exposure to deuterium amorphous carbon layers. The results show that the energy distribution for the physically sputtered single C atoms is almost consistent with the commonly used Thompson distribution and the assumed cosine distribution function.

A comprehensive, quantitative analysis that combines a hierarchical theoretical approach with experimental measurements is presented of the deformation behavior of coherently strained InAs/GaAs(111)A heteroepitaxial systems. The experimental measurements are found to be in excellent agreement with the calculated lattice interplanar distances and the corresponding strain fields in the thin mechanically unconstrained substrates considered in the theoretical analysis.

Deposition of MgO was studied to determine sputtering and in-plane texture control.

Direct molecular dynamics simulation of atomic deposition under realistic conditions is notoriously challenging because of the wide range of time scales that must be captured. Numerous simulation approaches have been proposed to address the problem, often requiring a compromise between model fidelity, algorithmic complexity, and computational efficiency. Coarse projective integration, an example application of the "equation-free" framework, offers an attractive balance between these constraints. Here, periodically applied, short atomistic simulations are employed to compute time derivatives of slowly evolving coarse variables that are then used to numerically integrate differential equations over relatively large time intervals. A key obstacle to the application of this technique in realistic settings is the "lifting" operation in which a valid atomistic configuration is recreated from knowledge of the coarse variables. Using Ge deposition on amorphous SiO2 substrates as an example application, we present a scheme for lifting realistic atomistic configurations comprised of collections of Ge islands on amorphous SiO2 using only a few measures of the island size distribution. The approach is shown to provide accurate initial configurations to restart molecular dynamics simulations at arbitrary points in time, enabling the application of coarse projective integration for this morphologically complex system. [ABSTRACT FROM AUTHOR]

The ability to predict the behavior of point defects in metals, particularly interstitial defects, is central to accurate modeling of the microstructural evolution in environments with high radiation fluxes. Existing interatomic potentials of embedded atom method type predict disparate stable interstitial defect configurations in vanadium. This is not surprising since accurate first-principles interstitial data were not available when these potentials were fitted. In order to provide the input information required to fit a vanadium potential appropriate for radiation damage studies, we perform a series of first-principles calculations on six different interstitial geometries and vacancies. These calculations identify the 〈111〉 dumbbell as the most stable interstitial with a formation energy of approximately 3.1 eV, at variance with predictions based upon existing potentials. Our potential is of Finnis-Sinclair type and is fitted exactly to the experimental equilibrium lattice parameter, cohesive energy, elastic constants and a calculated unrelaxed vacancy formation energy. Two additional potential parameters were used to obtain the best fit to the set of interstitial formation energies determined from the first-principles calculations. The resulting potential was found to accurately predict both the magnitude and ordering of the formation energies of six interstitial configurations and the unrelaxed vacancy ground state, in addition to accurately describing the migration characteristics of the stable interstitial and vacancy. This vanadium potential is capable of describing the point defect properties appropriate for radiation damage simulations as well as for simulations of more common crystal and simple defect properties. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations are performed to examine the effects of ion beams in selecting MgO island orientations during ion beam assisted deposition. Sputter yields are determined as a function of ion beam orientation for MgO islands of different sizes. While channeling does occur in small islands, the difference in sputter yields between channeling and nonchanneling orientations is much smaller in small islands than in larger islands or a continuous film. The ion beam is capable of disrupting the entire island structure at small island sizes, while channeling dependent sputtering occurs at larger island size. Since less sputtering occurs for channeling orientations, the ion beam produces an orientation-dependent island growth rate. This leads to island orientation-dependent nucleation rates. A new analytical model parameterized using the molecular dynamics sputter yield data is developed which predicts how growth conditions affect these island-orientation nucleation rates. Based upon these simulations and model results, we suggest a strategy to efficiently grow thin, highly textured MgO films. [ABSTRACT FROM AUTHOR]

Analyzes the energetics, interfacial stability, strain fields and film surface morphology in semiconductor heteroepitaxy. Application of continuum elasticity theory and atomistic simulations in the analysis; Computation of critical film thicknesses; Description of the atomistic simulation results; Results and discussion.