The structure of liquid Sn was studied by neutron scattering experiments in the widest temperature range that was ever performed. Though, on increasing temperature, the existence of the shoulder in the structure factor, S(Q), becomes less clear in the change of the overall shape of the S(Q), the structure related to this shoulder seems to be present even at 1873 K. The first-principle molecular-dynamics ͑FPMD͒ simulation was performed for the first time for liquid Sn by using the cell size of 64 particles. The calculated results well reproduced S(Q) obtained by the neutron experiments. The angle distribution, g (3) (,r c ), was evaluated for the angle between vectors from centered atom to other two atoms in spheres of cutoff radii r c 's. The g (3) (,r c ) shows that, with the decrease of r c from 0.4 to 0.3 nm, a rather sharp peak around 60°disappears and only a broad peak around 100°remains; the former peak may be derived from the feature of the closely packed structures and the latter one is close to the tetrahedral angle of 109°. In addition, the coordination number, n, of liquid Sn counted within the sphere of r c ϭ0.3 nm is found to be 2-3 and does not change with the increase of temperature even up to 1873 K. These facts indicate that at least the fragment of the tetrahedral unit may be essentially kept even at 1873 K for liquid Sn. For comparison, the FPMD simulation was performed for the first time also for liquid Pb. No sign of the existence of the tetrahedral structure was observed for liquid Pb. Unfortunately, the self-diffusion coefficients, D's, obtained from this FPMD for liquid Sn do not agree with those obtained by the microgravity experiments though the structure factors, S(Q)'s, are well reproduced. To remove the limitation of the small cell size of the FPMD, the classical molecular-dynamics simulations with a cell size of 2197 particles were performed by incorporating the present experimental structural information of liquid Sn. Obtained D's are in good agreement with the microgravity data.

The electrostatic levitation system, including its history and development, and techniques for non-contact thermophysical property measurements (density, ratio of isobaric heat capacity to hemispherical total emissivity, surface tension and viscosity) are reviewed. Thermophysical properties of refractory metals whose melting temperatures are over 2000 K have been measured with an electrostatic levitator. The experimental results for vanadium, zirconium, niobium, molybdenum, rhodium, ruthenium, iridium, tantalum and rhenium are presented. Comparison between theoretical calculations based on hard sphere model and measured data, as well as the necessity of microgravity conditions for this research is also discussed.

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New sample levitation initiation and imaging techniques for the processing of refractory metals with an electrostatic levitator furnace Rev.Thermophysical properties of molten refractory metals ͑titanium, zirconium, hafnium, and niobium͒ have been measured using a containerless method. Using an in-house developed electrostatic levitator, the density, the heat capacity, the entropy, the surface tension, and the viscosity of liquid phases have been measured over a wide temperature range. The measured data showed good agreement with theoretical calculations based on the hard sphere model.