Orientational disorder modeling in mixedhyphen;stack molecular crystals

摘要

The paper presents a simple model to mimic orientational disorder in molecular solids. The model is based on the concept of split molecule, an object which is a superposition of two molecules in orientations which are supposed to mimic orientational distribution. The split molecule is characterized by a disorder angle, an extra parameter which labels disorder states and allows one to calculate free energy of the crystal. The model is simple for applications illustrated by numerical calculations for chargehyphen;transfer crystals Ahyphen;TCNB and Nhyphen;TCNB, the family of solids where the onset of orientational disorder is responsible for structural phase transitions.