Neutron diffraction experiments for supercritical CO2 have been carried out over a wide range of Q (0.018≤Q≤30 Å−1) at ρ*=ρ/ρc=1.5, 1.2, 0.77, and 0.34 along an isotherm at 310 K (T*=T/Tc=1.02). The measurement enabled us to obtain quantitatively reliable radial distribution functions of the fluid including both short-ranged structure and long-ranged density fluctuation. The structure factor and radial distribution function showed the structural change from the attraction-predominant gaslike structure to the repulsion-predominant liquidlike one with increasing fluid density. With respect to the long-ranged structure, almost linear Ornstein–Zernike–Debye plots were obtained for S(Q) of the fluids at all densities. A plot of correlation length against reduced density seems to have a maximum at the critical density. A ratio, α(r), of the density fluctuation produced by the correlation within r to that to the infinity presented a new aspect of the density fluctuation. Molecular dynamics simulation has also been performed in order to investigate a molecular basis of the experimental radial distribution functions. The calculated GN(r)’s were in good agreement with experimental ones at each density. In laboratory space, a variety of orientational coordination structures are almost equally found in the fluid at all densities examined, while T-shaped structure is preferentially present in polar-angle space.

We have examined the relaxation behavior of alkali metal ions in lithium metasilicate glasses by means of molecular dynamics simulation. We have observed a change of slope of the mean squared displacement at ϳ300 ps. In shorter time regions, localized motion of lithium ions within neighboring sites is observed, which is caused by the small fracton dimension ͑fracton excitation͒. On the other hand, an accelerated motion of particles due to cooperative jumps is found, which characterizes the diffusion and conduction mechanisms of the alkali metal ions in longer time regions. The dynamics of accelerated motion is discussed in relation to Lévy flight dynamics. ͓S0163-1829͑97͒03510-8͔

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Thin films of Nd 3ϩ -substituted bismuth titanate, (Bi 4.00Ϫy ,Nd y )Ti 3.00 O 12 ͑BNT͒, Nd 3ϩ /V 5ϩ -cosubstituted bismuth titanate, (Bi 4.00Ϫy ,Nd y )(Ti 3.00Ϫx V x )O 12 ͑BNTV͒, and La 3ϩ -substituted bismuth titanate, (Bi 3.25 ,La 0.75 )Ti 3.00 O 12 ͑BLT͒ were fabricated on the (111)Pt/Ti/SiO 2 /(100)Si substrates by a chemical solution deposition technique. These films possessed random-oriented polycrystalline structure. The BNT film had larger remnant polarization ( P r ) than the BLT film; P r and coercive field (E c ) of the BNT film with yϭ0.50 were 32 C/cm 2 and 126 kV/cm, respectively. Furthermore, V 5ϩ substitution improved the P r value of the BNT film up to 37 C/cm 2 ͑BNTV film; yϭ0.50, xϭ0.02), while the BNTV film had an E c value of approximately 119 kV/cm which was similar to that of the BNT film. Ferroelectric properties of the Pb-free polycrystalline BNT and BNTV films are comparable with those of conventional Pb-based ferroelectric films like a lead zirconate titanate.

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