First‐Order Phase Transition in a Gas of Long Thin Rods

摘要: Onsager's prediction of a first‐order phase transition in gas long thin rods is verified by extensive calculations on simple model. The molecules are rectangular parallelepipeds, length l and square cross section d×d. molecular axes can point only three mutually perpendicular directions. Virial coefficients, up to the seventh, calculated exactly as functions orientation, limit l→ ∞, d→0, l2d=constant. predicted theory, based second virial approximation potential mean force space relative orientations, observed also when all coefficients seventh included. expansion appears converge well for isotropic phase; but properties anisotropic depend sensitively order approximation.