Structures of fused-dimer fluids: A new closure based on the potential distribution theorems

We carry out Monte Carlo (MC) simulation as well as solution of the Chandle r-Silbey-Ladanyi (CSL) equations with self-consistent closures for symmetri c hard dumbbells with bond lengths L = 0.1, 0.4, 0.6, 0.8, and 1.0. The con sistency conditions include the zero-separation theorems, the pressure cons istency (P-v = P-c), and the overlap conditions. Conventional closures, suc h as the Percus-Yevick closure, give the wrong sign (negative values) for t he unbonded bridge function B-00(r) for small bond lengths L < 0.8; the MC- determined behavior of B-00(r) being >0. This explains the failure of the c ommon liquid state closures for chain molecules. The CSL is solved with a s et of new closures. The new closure forms are flexible, and are required to satisfy the consistencies imposed. The results are at the same time consis tent and highly accurate. (C) 2001 American Institute of Physics.