Order-disorder phase transition in<i>p</i>-chloronitrobenzene studied by NQR and DTA

Abstract

A study of the temperature dependence of nuclear-quadrupolar resonance frequency (${\ensuremath{\nu}}_{\mathit{Q}}$) and spin-lattice relaxation time (${\mathit{T}}_{1}$) in p-chloronitrobenzene has revealed the existence of an order-disorder phase transition at ${\mathit{T}}_{\mathit{c}}$=282.6 K. Nitro groups reorient in the quenched disordered phase but such reorientations are not detected in the ordered phase. The entropy change, \ensuremath{\Delta}S, associated with the phase transition has been measured by differential thermal analysis and these results are discussed. \textcopyright{} 1996 The American Physical Society.