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Title: Static and dynamic correlation in lattice gas systems : an application to the intermetallic hydride ZrV2Hx
Author: Bull, Daniel James
ISNI:       0000 0001 2427 8953
Awarding Body: University of Salford
Current Institution: University of Salford
Date of Award: 2001
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CRT, a Monte Carlo program for the simulation of particle diffusion on a lattice gas is presented. The particle transition probability is calculated as a function of three parameters: lattice site energies, inter-particle interactions and neighbour jump-rates. GRT evaluates either the self correlation function, Gs(r,t), or the pair correlation function, G(r,t). A method is presented for interpreting these functions in terms of Sjnc(Q,w) and S CO h(Q,co), the incoherent and coherent quasielastic neutron scattering functions. GRT can also be used to calculate the static pair correlation function, G(r). which is related to SdifKQ), the diffuse structure factor from neutron and X-ray diffraction. It is demonstrated that, for diffusion in a lattice gas, the width of S COh(Q,co) is independent of concentration when there are no inter-particle interactions. When interactions are introduced, it is shown that the quasielastic line-width is reduced at points in reciprocal space corresponding to maxima in Sdifl GRT is subsequently applied to the intermetallic hydride (deuteride) ZrV 2 H(D) x . The form of G(r) with repulsive interactions is simulated as a function of concentration. This is compared to G(r), evaluated from neutron diffraction measurements on ZrV 2 D x? performed on the GEM diffractometer at ISIS, UK. For ZrV 2 H x, it is shown that S inc(Q,co), obtained from Monte Carlo simulations from diffusion, can be interpreted in terms of motion on two time-scales, corresponding to the convolution of a rapid local motion with a long-range translational diffusion. It is suggested that the geometry of the diffusion paths causes this behaviour. Incoherent quasielastic neutron scattering measurements on ZrV2 Hi i, measured on the INS time-of- flight spectrometer at the ILL, France, are presented. Again, motion on two time scales can be inferred from S,nc (Q,co). The characteristic jump-rates from the two types of motion are calculated and compared with other AB2 CIS Laves phase hydrides.
Supervisor: Not available Sponsor: Engineering and Physical Sciences Research Council (EPSRC)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Neutron scattering