Calculating the helical twisting power of chiral dopants

This paper describes a Monte Carlo simulation technique designed to predict the sign and magnitude of the helical twisting power, beta (M), of a chiral material. The method calculates the chemical potential difference, Delta mu, between a chiral dopant and its enantiomer when they are placed in a twisted nematic solvent. In the low concentration limit, Delta mu is directly proportional to beta (M). In the simulations presented, the chiral dopants are represented by atomistic models and a generic twisted nematic solvent composed of soft repulsive spherocylinders is employed. A free energy perturbation method is used to calculate Delta mu. Calculations are presented for five different dopant molecules with a wide range of helical twisting powers.