Phase behavior of the restricted primitive model and square-well fluids from Monte Carlo simulations in the grand canonical ensemble

Journal Article · Fri Jan 01 04:00:00 EST 1999 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.477798· OSTI ID:289228

Orkoulas, G; Panagiotopoulos, A Z ^[1]

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1. School of Chemical Engineering, Cornell University, Ithaca, New York 14853-5201 (United States)

Coexistence curves of square-well fluids with variable interaction width and of the restricted primitive model for ionic solutions have been investigated by means of grand canonical Monte Carlo simulations aided by histogram reweighting and multicanonical sampling techniques. It is demonstrated that this approach results in efficient data collection. The shape of the coexistence curve of the square-well fluid with short potential range is nearly cubic. In contrast, for a system with a longer potential range, the coexistence curve closely resembles a parabola, except near the critical point. The critical compressibility factor for the square-well fluids increases with increasing range. The critical behavior of the restricted primitive model was found to be consistent with the Ising universality class. The critical temperature was obtained as T{sub c}=0.0490{plus_minus}0.0003 and the critical density {rho}{sub c}=0.070{plus_minus}0.005, both in reduced units. The critical temperature estimate is consistent with the recent calculation of Caillol {ital et al.} [J. Chem. Phys. {bold 107}, 1565 (1997)] on a hypersphere, while the critical density is slightly lower. Other previous simulations have overestimated the critical temperature of this ionic fluid due to their failure to account for finite-size effects in the critical region. The critical compressibility factor (Z{sub c}=P{sub c}/{rho}{sub c}T{sub c}) for the ionic fluid was obtained as Z{sub c}=0.024{plus_minus}0.004, an order of magnitude lower than for nonionic fluids. {copyright} {ital 1999 American Institute of Physics.}

• OSTI ID: 289228
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 3 Vol. 110; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
CHEMICAL ENGINEERING
COMPRESSIBILITY
CRITICAL TEMPERATURE
DENSITY
FLUIDS
MONTE CARLO METHOD
PHASE DIAGRAMS
SIMULATION
SQUARE-WELL POTENTIAL