Screened dipolar interactions in some molecular crystals

• Published in: Chemical physics 1990-10, Vol.147 (1), p.35-43
• Main Authors: Munn, R.W., Hurst, M.
• Format: Article
• Language: English
• Subjects: Atomic and molecular physics; Effects of atomic and molecular interactions on electronic structure; Electronic structure of atoms, molecules and their ions: theory; Exact sciences and technology; Molecular solids; Physics
• ISSN: 0301-0104
• DOI: 10.1016/0301-0104(90)85018-R

Screened dipole energies and dipole electric fields are calculated for the crystals of HCN, meta- and para-nitroaniline, the nonlinear optical compounds POM, MAP and DAN, meta-dinitrobenzene, and acetanilide. Only para-nitroaniline is centrosymmetric, but all the crystals have significant negative dipole energies (of the order of −20 kJ mol −1) except for POM and metadinitrobenzene, where they are positive but small in magnitude. Local dipole fields are of the order of 10 GV m −1. The results assume that surface charge annuls any macroscopic dipole field. It is speculated that the observed preponderance of centrosymmetric crystals of polar molecules may reflect a favourable dipole energy in the initial crystal nucleus rather than the macroscopic crystal.