Multipole Interaction Effects on Cohesive and Anharmonic Properties of Alkali Cyanide Crystals

The cohesive and anharmonic properties of alkali cyanide crystals are investigated using a three‐body potential consisting of long‐range Coulomb and three‐body interactions, and the short‐range van der Waals attraction and overlap repulsion operative up to the second neighbour ions. The results on cohesive energy, compressibility, molecular force constant, and infrared absorption frequencies are in better agreement with their experimental data than those obtained earlier from a logarithmic potential. An overall systematic trend, followed by the values of third‐and fourth‐order elastic constants and the pressure and temperature derivatives of the second‐order elastic constants, is discussed.