HIGH-TEMPERATURE X-RAY-DIFFRACTION STUDY OF MELT STRUCTURE OF SILICON

The structure of molten silicon has been determined at three temperatu res of 1440, 1460 and 1520 degrees C by X-ray diffraction. All structu re factors indicate a characteristic small hump on the higher wave vec tor side of the first peak and such specific feature becomes slightly obscure as the temperature increases. A small peak is found in the reg ion between the first (0.245 nm) and second (0.55 nm) main peaks in th e pair distribution functions with a shallow minimum at about 0.35 nm. This is not observed in the pair distribution functions for usual mol ten metals. The coordination numbers in the near-neighbor region have been estimated by applying the interference function refining techniqu e and the results for the first two neighbors are 6.3 (4.6 + 1.7) at 1 440 degrees C, 5.7(4.5+1.2) at 1460 degrees C and 5.8 (4.4+1.4) at 152 0 degrees C. The present structural information is consistent with the recent results of density and electrical resistivity of molten silico n.