Vibrational spectroscopy at very high pressures. Part 6.—Infrared spectra of silver nitrate polymorphs

Abstract

The i.r. spectrum of silver nitrate has been studied as a function of temperature up to 184.5°C and at pressures up to 40 kbar in a diamond anvil cell. The characteristic features of phases I, II and III are reported. The spectra, and presumably the structures, of AgNO₃(II) and (III) are similar to those of KNO₃(I) and (IV) respectively. In accord with earlier work on the phase diagram, we find that a metastable phase, AgNO₃(V), can be obtained by rapid, rather than slow, application of pressure and have characterised it by i.r. spectroscopy at 60 kbar. Slight red shifts observed for AgNO₃(II) are accounted for using a theory of dipole-dipole coupling due to Decius.