Head-tail disorder and reorientation in solidN2O and CO: Dielectric study

The rate of molecular reorientation in solid ${\mathrm{N}}_2$O and $\alpha$-CO is obtained from audio-frequency dielectric measurements. Both sets of data obey the Arrhenius expression. The rates extrapolate to mean reorientation times of one hour at temperatures well above the predicted dipolar ordering temperatures. Hence, the residual entropy in these solids is shown to be a kinetic effect. The size of the reorientational part of the susceptibility and the best residual entropy values show that ${\mathrm{N}}_2$O has no short-range dipolar order while solid $\alpha$-CO has a significant antiferroelectric short-range order. The mechanism of reorientation in $\alpha$-CO is shown to be 180° rotations; ${\mathrm{N}}_2$O is believed to reorient with the aid of some intrinsic defect.