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There have been many studies applying atomistic simulation techniques to investigate the structure and energetics of surfaces and interfaces. Almost all start by de®ning the basic structure of the interface, which is then simulated by static or dynamical methods. A different approach is adopted here, where we allow interfacial structures to evolve during the course of the simulation. In particular, three atomistic simulation methodologies for constructing models for thin ®lm interfaces have been developed, including `atom deposition', where the thin ®lm is `grown' by sequentially depositing atoms onto a support material to obtain information on nucleation and growth mechanisms; `layer-by-layer' growth, where monatomic layers of a material are successively deposited on top of a substrate surface; and ®nally, `cube-on-cube' whereby the whole of the thin ®lm is placed directly on top of the substrate, before dynamical simulation and energy minimisation. The methodologies developed in this study provide a basis for simulating the nucleation, growth and structure of interface systems ranging from small supported clusters to monolayer and multilayer thin ®lm interfaces. In addition, the layer-by-layer methodology is ideally suited to explore the critical thickness of thin ®lms. We illustrate these techniques with studies on systems with large negative mis®ts. The calculations suggest that the thin ®lms (initially constrained under tension due to the mis®t) relax back to their natural lattice parameter resulting in the formation of surface cracks and island formation. The cube-on-cube methodology was then applied to the SrO/MgO system, which has a large (z20%) positive mis®t. For this system, the SrO thin ®lm underwent an amorphous transition which, under prolonged dynamical simulation, recrystallised revealing mis®t-induced structural modi®cations, including screw-edge dislocations and low angle lattice rotations.

The applicability of ionic liquids within the nuclear industry has been investigated. The radiation stability of ionic liquids containing dialkylimidazolium cations has been tested through with alpha, beta and gamma irradiation. The results of these tests suggest that imidazolium salts have stabilities similar to alkylbenzenes and greater than tetrabutylphosphate / odorless kerosene (TBP/OK) mixtures. The oxidative dissolution of uranium dioxide and the anodic dissolution of uranium metal and plutonium metal have been carried out in various ionic liquid media 162

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Thin film solar cells based upon CdS-CdTe heterojunctions have become an important alternative to silicon based devices. The film structures formed during fabrication are critical to cell efficiency and thus their study is fundamental to improving device performance. We have used synchrotron x-ray diffraction to investigate the effect of a post deposition anneal upon the film structures and, in particular, have examined the dynamic formation of intermixed regions adjacent to the original, metallurgical interface. Our results have enabled us to produce a dynamic model for the structural changes which includes the extent of interdiffusion. We show that, for a 400 nm CdTe film in the presence of chlorine, the original CdS and CdTe layers are completely transformed into layers with average compositions CdS 0.93 Te 0.07 and CdTe 0.94 S 0.06 , respectively. We present evidence that the interdiffusion occurs during or following a recrystallization and that, to a limited extent, these changes also occur without chlorine.

A radiological dispersal device (RDD) is a simple weapon capable of causing human harm, environmental contamination, disruption, area denial, and economic cost. It can affect small, large, or long areas depending on atmospheric stability. The risk of developing a radio-induced cancer depends on exposure, and an effective response depends upon available timely guidance. This article proposes and demonstrates a convergence of three different capabilities to assess risk and support rapid safe resource efficient response. The three capabilities that are integrated are Hotspot for dispersion, RERF for epidemiological risk, and RESRAD-RDD for response guidance. The combined methodology supports decisions on risk reduction and resource allocation through work schedules, the designation and composition of response teams, and siting for operations. In the illustrative RDD scenario, the contamination area for sheltering, evacuation, and long-term public concern was greatest for calm atmospheric conditions, whilst close-quarter responders faced highest dose rates for neutral atmospheric conditions. Generally, the risks to women responders were found to be significantly greater than for men, and the risks to 20-year-old responders were three times that of their 60-year-old counterparts for similar exposure.

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