The incommensurate phase II of biphenyl

Abstract

The authors discuss in detail the incommensurate phase II of biphenyl, in which the modulation vector is not along one major direction of the reciprocal lattice. This double incommensurateness is due to the interplay of the molecules' twists, translations and librations. They calculate the intermolecular interactions by computer modelling and analyse their implications. Calculations are carried out to demonstrate that this model explains the double incommensurateness. Furthermore they clarify the ambiguity concerning the structure of the modulation in phase II, and prove that it must be 'stripe'-like rather than 'quilt'-like. The implications of this result for the transition between phases II and III are discussed.