The Raman spectrum of a ${\mathrm{KNO}}_3$ single crystal was measured at both room and liquid-nitrogen temperatures. Lattice-dynamical calculations, based on the rigid-ion approximation and empirical potentials, were performed. The possibility of a phase transition at 217 K was investigated by measuring the temperature dependence of the Raman spectrum.

• Received 19 August 1991

DOI:https://doi.org/10.1103/PhysRevB.45.2142