Microscopic Model of NaNO2Based on Reorientations and Translations

Abstract

Starting from an atomistic sterical hindrance potential, translational and orientational motion of the N${\mathrm{O}}_2$ group in the deformable lattice are described. The reorientations of the N${\mathrm{O}}_2$ group in the paraelectric phase occur essentially by rotations around the crystallographic $\overrightarrow{\mathrm{c}}$ axis, in agreement with slow or zero-frequency experiments. It is explained why high-frequency optical methods lead to the incorrect conclusion that reorientations take place around the $\overrightarrow{\mathrm{a}}$ axis. The collective interaction of translations and rotations is discussed.