Seasonal variation in exploitative competition between honeybees and bumblebees.

Honeybees (Apis mellifera) and bumblebees (Bombus spp.) often undergo exploitative competition for shared floral resources, which can alter their foraging behaviour and flower choice, even causing competitive exclusion. This may be strongest in summer, when foraging conditions are most challenging for bees, compared to other times of the year.

Reaction pathways in atomistic models of thin film growth.

The atomistic processes that form the basis of thin film growth often involve complex multi-atom movements of atoms or groups of atoms on or close to the surface of a substrate. These transitions and their pathways are often difficult to predict in advance. By using an adaptive kinetic Monte Carlo (AKMC) approach, many complex mechanisms can be identified so that the growth processes can be understood and ultimately controlled.

Using atomistic simulations to model cadmium telluride thin film growth.

Cadmium telluride (CdTe) is an excellent material for low-cost, high efficiency thin film solar cells. It is important to conduct research on how defects are formed during the growth process, since defects lower the efficiency of solar cells. In this work we use computer simulation to predict the growth of a sputter deposited CdTe thin film.

Influence of the prefactor to defect motion in α-Iron during long time scale simulations.

We present a study of the influence of the prefactor in the Arrhenius equation for the long time scale motion of defects in α-Fe. It is shown that calculated prefactors vary widely between different defect types and it is thus important to determine these accurately when implementing on-the-fly kinetic Monte Carlo (otf-KMC) simulations. The results were verified by reproducing many events using Molecular Dynamics (MD) and Temperature-Accelerated Dynamics (TAD).

Modelling the growth of ZnO thin films by PVD methods and the effects of post-annealing.

Results are presented for modelling of the evaporation and magnetron sputter deposition of Zn(x)O(y) onto an O-terminated ZnO (0001¯) wurtzite surface. Growth was simulated through a combination of molecular dynamics (MD) and an on-the-fly kinetic Monte Carlo (otf-KMC) method, which finds diffusion pathways and barriers without prior knowledge of transitions. We examine the effects of varying experimental parameters, such as substrate bias, distribution of the deposition species and annealing temperature.

A theoretical study of intrinsic point defects and defect clusters in magnesium aluminate spinel.

Point and small cluster defects in magnesium aluminate spinel have been studied from a first principles viewpoint. Typical point defects that occur during collision cascade simulations are cation anti-site defects, which have a small formation energy and are very stable, O and Mg split interstitials and vacancies. Isolated Al interstitials were found to be energetically unfavourable but could occur as part of a split Mg-Al pair or as a three atom-three vacancy Al 'ring' defect, previously observed in collision cascades using empirical potentials.

Improved grid-based algorithm for Bader charge allocation.

An improvement to the grid-based algorithm of Henkelman et al. for the calculation of Bader volumes is suggested, which more accurately calculates atomic properties as predicted by the theory of Atoms in Molecules. The CPU time required by the improved algorithm to perform the Bader analysis scales linearly with the number of interatomic surfaces in the system.

Molecular dynamics simulations of nanoindentation and nanotribology.

We present results of parallel molecular dynamics simulations of nanoindentation and nanotribology experiments. The models we have developed describe both the sample and the indenter atomistically and model the effect of the cantilevers in an atomic force microscope through the use of springs. We show that the simulations are in good qualitative agreement with experiment and help to elucidate many of the mechanisms that take place during these processes.

Molecular-dynamics simulations of sputtering.

The use of molecular-dynamics simulations to understand the ejection processes of particles from surfaces after energetic ion bombardment is discussed. Substrates considered include metals, covalent and ionic materials, polymers and molecular solids. It is shown how the simulations can be used to aid interpretation of experimental results by providing the underlying mechanisms behind the ejection processes.

Scaling relations for implantation of size-selected Au, Ag, and Si clusters into graphite.

The deposition of size-selected clusters represents a new route to the fabrication of truly nanometer-scale surface architectures, e.g., nanopores.