Constant pressure (NPH) ensemble molecular dynamics calculations have been used to study the cubic to orthorhombic phase transition that occurs upon cooling potassium cyanide at low pressures. A rigid ion model consisting of interionic electrostatic terms plus nonbonded atomndash;atom interactions has been found to yield an almost quantitative account of the transition. In particular, the extreme softening of the shear elastic constantC44and the anomalous dispersion of the transverse acoustic phonons propagating along the crystal lsqb;100rsqb; direction in the cubic phase are well reproduced.
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