A molecular model of p-terphenyl and its disorder-order transition

An all-atom empirical potential is presented for p-terphenyl and compared w ith models in the literature. The model predicts correctly the structure of the crystal above and below the disorder-order transition. The ring flip d ynamics in the model is in good qualitative and fair quantitative agreement with X-ray, neutron and NMR measurements: far above the transition, ring f lipping is a local, activated process in an effective double-well potential ; near the transition fluctuations grow in size and lifetime; below the tra nsition, individual phenyl rings are locked in four inequivalent positions. (C) 1999 Elsevier Science B.V. All rights reserved.