Mathemateg a Ffiseg / Mathematics & Physicshttp://hdl.handle.net/2160/142016-04-25T18:22:35Z2016-04-25T18:22:35ZStructure factor changes in supercooled yttria-aluminaWilding, Martin C.Greaves, G. NevilleVan, Quang VuMajérus, OdileHennet, Louishttp://hdl.handle.net/2160/424732016-03-24T16:19:15Z2009-01-01T00:00:00ZStructure factor changes in supercooled yttria-alumina
Wilding, Martin C.; Greaves, G. Neville; Van, Quang Vu; Majérus, Odile; Hennet, Louis
Paniago, Rogiero Magalhaes
Changes in the structure factor of yttria-alumina liquids have been identified in the supercooled range. Different inter-polyhedral configurations between AlO4 and YO6 groups distinguish low density and high density liquid phases. The coexistence of phases at high temperatures have been identified in simultaneous measurements of small angle x-ray scattering.
2009-01-01T00:00:00ZA Noncommutative de Finetti Theorem: Invariance under Quantum Permutations is Equivalent to Freeness with AmalgamationKöstler, ClausSpeicher, Rolandhttp://hdl.handle.net/2160/424282016-03-24T15:11:37Z2009-12-31T00:00:00ZA Noncommutative de Finetti Theorem: Invariance under Quantum Permutations is Equivalent to Freeness with Amalgamation
Köstler, Claus; Speicher, Roland
We showthat the classical de Finetti theorem has a canonical noncommutative counterpart if we strengthen 'exchangeability' (i.e., invariance of the joint distribution of the random variables under the action of the permutation group) to invariance under the action of the quantum permutation group. More precisely, for an infinite sequence of noncommutative random variables (xi )i?N, we prove that invariance of the joint distribution of the xi's under quantum permutations is equivalent to the fact that the xi 's are identically distributed and free with respect to the conditional expectation onto the tail algebra of the xi 's.
2009-12-31T00:00:00ZMolecular Dynamics Study of Ion Diffusion in Glassy MaterialsFlikkema, EdwinGreaves, NevilleZhou, Zhongfuhttp://hdl.handle.net/2160/423182016-04-13T23:12:40Z2011-06-30T00:00:00ZMolecular Dynamics Study of Ion Diffusion in Glassy Materials
Flikkema, Edwin; Greaves, Neville; Zhou, Zhongfu
2011-06-30T00:00:00ZGraph-based global optimization of fully-coordinated cluster geometriesFlikkema, E.Bromley, S. T.http://hdl.handle.net/2160/423142016-04-13T23:11:19Z2009-03-17T00:00:00ZGraph-based global optimization of fully-coordinated cluster geometries
Flikkema, E.; Bromley, S. T.
We present a detailed global optimization study of cluster geometries with silica nano-clusters (SiO$_2$)$_N$ as a specific example. In an earlier study (Phys. Rev. Lett., 95: 185505, 2005) we used the Basin Hopping methodology combined with an empirical potential to find low-energy cluster geometries. These often exhibit defects such as dangling oxygens. In this contribution we will present an algorithm for global optimization of cluster geometries, which limits the search specifically to fully-coordinated cluster geometries, i.e. defectless clusters where each silicon atom is bonded to 4 oxygen atoms and each oxygen atom is bonded to 2 silicon atoms. This algorithm is based on performing Monte Carlo moves on the set of graphs rather than in coordinate space, the graph being the network of silicon-oxygen bonds. Promising low-energy geometries are selected for refinement using Density Functional Theory calculations. Clusters of a size of up to 30 SiO$_2$ units have been studied. The properties of low-energy fully-coordinated clusters will be compared to those of clusters with defects.
2009-03-17T00:00:00Z