The Phase Transition of Crystalline Potassium Thiocyanate, KSCN. II. X-Ray Study

The phase transition of potassium thiocyanate has been investigated by the X-ray diffraction. It was confirmed that it is an order-disorder type transition with regard to the orientation of the thiocyanate ions. The temperature dependence of the ordering and the anomalous volume expansion near the transition temperature seem capable of being interpreted by the molecular field approximation if the volume dependence of the interaction energy is taken into account.