Estimation of effective diameters for molecular fluids

Journal Article · Thu Feb 08 00:00:00 EST 1990 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100366a003· OSTI ID:7107987

Ben-Amotz, D; Herschbach, D R ^[1]

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1. Exxon Research and Engineering Co., Annandale, NJ (USA)

Effective diameters of atoms and molecules can typically be estimated within about 1% from equation-of state or compressibility data. These estimates correlate well with critical volumes, with molar refractivities, and with tabulated van der Waals volume increments. The correlations hold well even for markedly aspherical or polar molecules. Comparison of a simple perturbed hard-sphere equation of state (the Carnahan-Starling-van der Waals equation, denoted CS-vdW) with molecular dynamics simulations shows that surprisingly good values for both the Lennard-Jones radius and well depth (typically within 1% for {sigma}{sub LJ}, 10% for {epsilon}{sub LJ}) can be obtained by using pressure-density isotherms or equivalent data. Together with empirical correlations, this permits the LJ potential parameters to be estimated simply from the density (at atmospheric pressure) and the heat of vaporization or boiling point temperature. The temperature dependence of the effective diameter can be estimated from a simple model originally introduced by Boltzmann. More sophisticated perturbative theories of liquids predict a small additional density dependence of the effective diameter. Simple analytical expressions for these theoretical models are presented. In particular, the CS-vdW equation is found to predict reliable absolute densities (within 1%) for liquids at high pressures where direct measurements become difficult.

• OSTI ID: 7107987
• Journal Information: Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 94:3; ISSN JPCHA; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
99 GENERAL AND MISCELLANEOUS
990200 -- Mathematics & Computers
ALCOHOLS
ALKANES
ANALYTIC FUNCTIONS
CALCULATION METHODS
DATA
DATA ANALYSIS
DENSITY
ENTHALPY
EQUATIONS
EQUATIONS OF STATE
FLUIDS
FUNCTIONS
HIGH PRESSURE
HYDROCARBONS
HYDROXY COMPOUNDS
INFORMATION
LENNARD-JONES POTENTIAL
LIQUIDS
MATHEMATICAL MODELS
NUMERICAL DATA
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
POTENTIALS
SUPERCRITICAL STATE
TEMPERATURE DEPENDENCE
THEORETICAL DATA
THERMODYNAMIC PROPERTIES
TRANSITION HEAT
VAPORIZATION HEAT