Fig. 6.
Fully atomistic MD simulations of equilibrium nematic phases at T = 370 K in CB6CB, a linear molecule (A), and CB7CB, a bent molecule (B), showing a periodic box of a nominally 5.6 × 5.6 × 8.0 nm dimension. Initial equilibration is carried out with opposed forces in the z direction on the molecular ends, giving a form of field-induced nematic monodomain. As these forces are relaxed, CB6CB remains a nematic, with n along z (A), whereas CB7CB relaxes into a heliconical TB structure, of pitch pTB = 8.1 nm and cone angle θTB = 25° (B). The periodic box adjusts in length along z to equilibrate the pressure. (C and D) Example configurations showing explicitly the orientations ni of the biphenyl groups that determine the half-molecular director field n. CB6CB shows conventional nematic ordering whereas there is clearly heliconical ordering in CB7CB (SI Appendix, Figs. S17 and S18).