The acoustic and neutron scattering investigations of NH₄SCN phase diagram

Abstract

The aim of the present work is the investigation of the p-T boundary of the monoclinic III-orthorhombic II phase transition of NH₄SCN up to 77 K in order to search for a possible triple point [1] and the revelation of possible peculiarities of the NH₄SCN p-T diagram near 200K [2]. The NH₄SCN samples were prepared from a fine-grained powder-like material of high purity. Because of its high hygroscopicity the powder was dried at 75°C. Acoustic studies were made at pressures up to 1.6 GPa over a temperature range 77–323 K using the ultrasonic method [3–5]. The neutron scattering measurements were carried out over a temperature range 10 to 430 K [6] on the NERA-PR time-of-flight (TOF) neutron spectrometer placed at the IBR-2 high flux pulsed reactor of JINR.