The migration pathway and energy of an oxygen vacancy were calculated in quartz, stishovite and cristobolite using an empirical potential. For comparison the minimum energy pathway in quartz was calculated using density functional theory. The differences between the two methods show that although the energies of both approaches are similar, the pathways go through different intermediate states ...

This paper presents an algorithm for task allocation in groups of homogeneous robots. The algorithm is based on vacancy chains, a resource distribution strategy common in human and animal societies. We define a class of task-allocation problems for which the vacancy chain algorithm is suitable and demonstrate how Reinforcement Learning can be used to make vacancy chains emerge in a group of Beh...

Point defect species and concentrations in metastable Fe-C alloys are determined using density functional theory and a constrained free-energy functional. Carbon interstitials dominate unless iron vacancies are in significant excess, whereas excess carbon causes greatly enhanced vacancy concentration. Our predictions are amenable to experimental verification; they provide a baseline for rationa...

The diffusion of Ne in Ag is investigated by bombarding Ag sheet with energetic Ne ions and observing the Ne release during constant temperature anneals; giving D=2.5 * 1.5 exp (-59.5 5 2.0 x 103 Cal/mole/ RT), for volume diffusion. The activation energy is not consistent with previous values found for other inert gases in Ag but agrees with the predictions of impurity diffusion theory for diff...