PRE-MELTING MODE IN THE DISORDERED KNO_3 CRYSTAL OBSERVED BY THE LOW-FREQUENCY RAMAN SCATTERING(Session I : Cross-Disciplinary Physics, The 1st Tohwa University International Meeting on Statistical Physics Theories, Experiments and Computer Simulations)

Abstract

On heating, potassium nitrate, KNO_3 undergoes a structural phase transition from the orthorhombic structure (phase II) to the trigonal structure (phase I) at 403 K(T_c) and melts at 606 K(T_m). The central peak in low-frequency Raman scattering spectra of KNO_3 was studied from room temperature up to 130 K above the melting point T_m. A drastic growth was observed with increasing temperature below and above T_m. The spectra were numerically analyzed and the results revealed that the central peak of KNO_3 consists of two spectral components; one is common between the solid state phase I and the molten state, and the other is sensitive for melting process.