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.
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