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The structure of liquid deuterium fluoride has been measured using pulsed neutron diffraction and high energy x-ray diffraction techniques as a function of temperature. The neutron experiments were performed at T=296±2 K, 246±2 K, and 193±2 K and the x-ray measurements carried out at 296±2 K and 195±2 K. The x-ray pair correlation functions, which are dominated by fluorine-fluorine interactions, show the first peak at ∼2.53 ±0.05 &Aangst; remains very nearly invariant with decreasing temperature. Peaks around 4.5 and 5.0 &Aangst; also appear at both temperatures in the x-ray data. In contrast, the intermolecular peaks in the total neutron pair correlation function show that significant systematic local structural changes occur as the temperature is lowered. The first intermolecular peak position shortens from 1.64±0.05 &Aangst; at 296 K to 1.56±0.05 &Aangst; at 195 K. Although there are overlapping contributions from the intermolecular hydrogen-fluorine and hydrogen-hydrogen correlations, it is clear that the temperature dependent structural changes are largely due to a rearrangement of the deuterium atom positions in the fluid. By comparison with partial structure factor data the hydrogen bonds appear to become more linear at lower temperatures. [ABSTRACT FROM AUTHOR]

The results and reverse Monte Carlo analysis of diffraction measurements of BF[sub 3] in the liquid and supercritical state are presented. Liquid BF[sub 3] displays order only in the first coordination sphere around the average molecule and there is no intermediate range order. Liquid BF[sub 3] is thus not a layered liquid. Angular analysis using reverse Monte Carlo modeling shows that the dominant structural motif in the solid state, that of pseudo trigonal bipyramidal [3+2] coordination at B is partially retained in both the liquid and supercritical phase, though in the latter, this structural preference is greatly reduced. The structure of the supercritical phase retains the same intermolecular contact as the liquid phase, though the structural sites and population of these sites is much more widely distributed. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The total structure factors, S(Q) of 50:50 mole% CaO:Al2O3- and 67:33 mole% SrO:Al2O3-composition liquids have been determined by neutron diffraction. Measurements were made on laser beam-heated liquids at 2000-2100 K held in an aerodynamic levitator. Pure vanadium levitation nozzles were used. Reduction of the nozzle wall thickness decreased attenuation of scattered neutrons to give a two-fold increase in signal intensity. The liquids are comprised of predominantly 4-coordinated aluminum and 6- and higher-coordinated group II metal ions. [ABSTRACT FROM AUTHOR]

Quasicrystals, formed during the primary crystallization stage of annealing Zr70-XCu25Pt5AlX metallic glasses, decrease in size from 100 to 5 nm as the Al content is increased from 8 to 10 at. %. The glass transition and crystallization processes during annealing at fixed heating rate were found to be influenced by the thermal history of the melt. Pair distribution function analyses of neutron scattering data revealed that the broad peak from the nearest atomic pairs separates into multiple peaks with lower melt quenching temperatures (TL). These results suggest that the short-range order is enhanced with decreased TL. Such ordered regions remain in the glass upon quenching and contribute to nanoquasicrystal formation upon heating. [ABSTRACT FROM AUTHOR]