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Effect of molecular elongation on the quadrupolar free energy in diatomic fluids

1988; Taylor & Francis; Volume: 65; Issue: 4 Linguagem: Inglês

10.1080/00268978800101421

1362-3028

Michael Bohn, Johann Fischer, J. M. Haile,

Spectroscopy and Quantum Chemical Studies

This paper reports results obtained from computer simulations of pure fluids composed of two-centre Lennard-Jones plus point quadrupole molecules. Simulations were performed over a range of quadrupole moments 0 ⩽ Q 2 ⩽ 4 and a range of molecular elongations 0 ⩽ l ⩽ 0·793. The principal results reported are values of the quadrupolar contribution to the Helmholtz free energy AQ , which was computed via Kirkwood's coupling parameter method. We show how AQ responds to changes in both Q and l. Results are also presented for the configurational internal energy, the quadrupolar internal energy, and site-site pair distribution functions. The simulation results are used to test two forms of first-order perturbation theory; neither form of the theory satisfactorily predicts the simulation results when both the quadrupole moment and the molecular elongation are large.