Quantum effects and orientational ordering in adsorbed layers of linear molecules

Abstract

Abstract We study the influence of quantum fluctuations on the herringbone transition in adsorbed complete √3‐mono‐layers of diatomic molecules. Using Path‐Integral Monte Carlo simulations for rotations, we can quantify the shift of the transition temperature for a highly realistic model to describe N 2 on graphite. In addition, the zero‐point motion of the librating molecules depresses the ground‐state order parameter. We compare the benchmark data to quadratic Feynman‐Hibbs effective potential simulations and to a quasiharmonic approximation. Using a simplified model for this transition, we study systematically quantum effects being relevant for lighter molecules. Depending on the rotator's rotational constant, we find re‐entrant orientational quantum melting or even the suppression of orientational order.