Compressibility of Water and Organic Liquids from Monte Carlo Simulations: Support for the Lennard-Jones 12–6 Potential

Abstract

Densities of organic liquids and water have been computed at pressures from −250 atm to 10,000 atm using Monte Carlo (MC) simulations in the NPT ensemble with the OPLS and TIPnP force fields. Comparisons with experimental data show average discrepancies of ca. 1%. It is demonstrated that the fluctuation formula for compressibility from statistical mechanics yields results in close accord with the slope of the density versus pressure results from the present long MC simulations. Definitive results for the isothermal compressibility of the TIP3P, TIP4P, and TIP5P water models at 25 °C are reported as 53, 50, and 58 ± 1 in units of 10–6 atm–1, respectively, while the experimental value is 45.8. A straightforward, versatile procedure is provided for computing a fundamental property of fluids with applications for fuel science, hydraulic systems, acoustics, and force-field evaluation. The results also support the validity of the use of the Lennard-Jones 12–6 potential for describing interatomic nonbonded interactions by reproducing experimental density data through the full fluid range up to ca. 40% compressions.