Temperature dependence of liquid Si (l-Si) density has been interested from view point of both industrial applications and condensed matter sciences. These are due to that Si has an unusual property at melting. When Si crystals melt, unlike other metals, their volume expands about 10 percent. Therefore l-Si has been interested from atomic structure, thus the density and the structure of supercooled l-Si have been measured by using some levitation technique, electromagnetic levitation (EML), electrostatic levitation (ESL) and conical-nozzle gas levitation (CNL) technique. Using ESL technique, the results of temperature dependence of l-Si density showed quadratic temperature dependence. On the other hand, quadratic temperature dependence of l-Si density has not been confirmed in the results of measurements using EML technique, because the results of EML technique had large variation in temperature dependence. The existing the maximum density in undercooled regions expected from the first principle molecular dynamics (FPMD) simulations. We performed the precise measurements of density of supercooled l-Si using EML technique with static magnetic fields and also performed structure analysis of l-Si by x-ray diffraction combined with the FPMD. The observed density of supercooled l-Si density and the FPMD results shows good agreement in the temperature range from 1450K to 1800K. The structure of supercooled l-Si was also good agreement between experiments and FPMD simulations. Based on these results, we discuss about the existence of density maximum in supercooled l-Si which is well known in water (H2O) at 4°C.
