Lattice dynamics of orthorhombic C2H2

Abstract

Stable lattice dynamical models of orthorhombic C2H2 are developed from those devised by Hirshfeld and Mirsky (1979) for the cubic phase. These satisfactorily reproduce measured phonon frequencies but cannot account for the crystal cohesive energy. Models are also identified based on the work of Nyberg and Faerman (1989) the principal difference being bond- rather than atom-centred short-range interactions. These yield acceptable crystal energies. All models have physically realistic molecular quadrupole moments.