PRESSURE-INDUCED STRUCTURE CHANGE OF MOLTEN KCL

Energy-dispersive X-ray diffraction experiments of molten KCI under hi gh pressure have been carried out by using synchrotron radiation. The diffraction profiles of molten KCl were acquired just above the meltin g temperature of KCl up to 4 GPa. The reduced structure factor S(Q)'s for molten KCI do not show any change in their primary features, excep t for a gradual increase in the first peak intensity with increasing p ressure. This implies that molten KCl does not show a first-order phas e transition, such as the B1-B2 transition, found in solid KCl, but th at the local structure in molten KCl must be changed by compression. A ccording to a molecular-dynamics simulation, this change of S(Q) can b e explained by a continuous increase in the coordination number of the nearest-neighbor ions in molten KCl with pressure.