Second-rank orientational order parameters, P2, were calculated for each trajectory frame as -2× the middle eigenvalue of the ordering tensor, Qαβ, defined by Equation , where N is the number of molecules, j is the molecule number in the simulation, α and β represent the Cartesian x, y and z axes, δ is the Kronecker delta, and a is the component of the principal molecular axis vector defined in the text. The director at each frame was defined as the eigenvector associated with the largest eigenvalue of the ordering tensor.