William B. Streett

Experimental Study of the Equation of State of Liquid Krypton

The gas expansion method has been used to measure the density of liquid krypton at 11 temperatures from 120 to 220°K and at pressures up to 3680 atm. The results have been fitted to the Strobridge equation, which has been used to estimate, at regular intervals of pressure and temperature, the following properties: density, isothermal compressibility, thermal expansion coefficient, thermal pressure coefficient, configurational internal energy, and entropy relative to the saturated liquid. The equation of state results, together with estimated values of the third virial coefficient and published values of vapor pressure, second virial coefficient, and sound velocity in the liquid phase, have been used to estimate the following properties of the saturated liquid: enthalpy of vaporization, configurational internal energy, isothermal compressibility, thermal expansion coefficient, thermal pressure coefficient, adiabatic compressibility, and specific heats. The linear dependence of configurational internal ener...

An experimental study of the equation of state of liquid xenon

The gas-expansion method has been used to measure the density of liquid xenon at 17 temperatures from 165.00 to 289.74K and at pressures up to 3815 atm. The 530 experimental points have been fitted to the Strobridge equation, which has been used to estimate, at regular intervals of pressure and temperature, the following properties: density; isothermal compressibility; thermal expansivity; thermal pressure coefficient; configurational internal energy; and entropy relative to the saturated liquid. Within the range of the experiments, the configurational internal energy is very nearly a linear function of density. The experimental results, together with estimated third virial coefficients and published values of vapour pressure, second virial coefficient, and sound velocity in the liquid phase, have been used to estimate the following properties of the saturated liquid on the liquid-vapour coexistence curve: enthalpy of vaporization; configurational internal energy; isothermal compressibility; thermal expansivity; thermal pressure coefficient; adiabatic compressibility; and heat capacity. The results have been use, together with published pressure, temperature data for the melting curve, to estimate the following properties of the saturated liquid on the liquid-solid coexistence curve: density; isothermal compressibility; thermal expansivity and thermal pressure coefficient.

Freezing and melting properties of the Lennard‐Jones system

Using Monte Carlo simulations, we investigate average molecular arrangements that occur with the fluid‐solid transition in a classical Lennard‐Jones system. The crystalline order of the solid phase is explicitly shown by the angularly averaged molecular correlation functions which, in the solid, exhibit a behavior not observed in the fluid. The pair and triplet correlation functions delineate the crystalline pattern of the ordered phase out to internuclear separations of many nearest‐neighbor distances. A molecular criterion for freezing is reported which claims a proportionality between the values of the pair correlation function in the fluid at the positions of the first and second nearest neighbors. The general behavior of the triplet correlation function in the fluid phase is interpreted. We also compare predictions for melting pressures and the densities of the coexisting fluid and solid phases.

Comparisons of Monte Carlo and RISM calculations of pair correlation functions

The solutions of the RISM integral equation are compared with Monte Carlo results for three hard‐core diatomics, including both homonuclear and heteronuclear models. The comparison shows that the RISM theory is qualitatively reliable and that the sizes of quantitative errors in the theory are predicted accurately by internal consistency tests.

Experimental Study of the Equation of State of Liquid Argon

The density of liquid argon has been measured at 10 temperatures from 100.9° to 143.1°K and at pressures up to 680 atm. The results have been expressed as an equation of state in the form of a double Chebyshev expansion. This equation has been used to estimate, at regular intervals of temperature and pressure, the following properties: molar volume, isothermal compressibility, coefficient of thermal expansion, thermal pressure coefficient, and configurational internal energy. Comparison is made between the present results and previous work on liquid argon, both at the saturation vapor pressure and at higher pressures.

Monte Carlo studies of the fluid‐solid phase transition in the Lennard‐Jones system

Monte Carlo calculations for 108‐ and 256‐particle Lennard‐Jones systems have been carried out at 140 temperature‐density points in the vicinity of the fluid‐solid phase transition. Several types of initial configurations have been used, including fcc lattice arrays, disordered arrays, and combinations of lattice and disordered arrays. The results of runs at high densities show that for small periodic systems the calculations are dependent on the initial configuration and that such systems can exist in many different metastable states from which minimum energy states are not accessible in runs of the order of 106 to 107 configurations. In the vicinity of the smallest density at which the fcc lattice is stable, the calculated pressure‐volume curve exhibits many of the features of a ``van der Waals loop; however, because a single phase is thermodynamically unstable over part of this region, the loop cannot be completely resolved through machine calculations. The use of the van der Waals loop to estimate t...

The 14N2/15N2 and 14N2/14N15N liquid-vapour isotope separation factor

A theoretical calculation of the 14N2/15N2 and 14N2/14N15N liquid-vapour isotope separation factors using a diatomic, or atom-atom potential is undertaken. The results show that this potential is capable of representing the isotope separation factors with some permissible variation in the parameter set.

Sound Velocity, Adiabatic Compressibility, and Specific Heat of Liquid and Dense Fluid Krypton

The sound velocity, W, in liquid and dense fluid krypton has been measured with an estimated accuracy of 0.2%, using a double‐transducer acoustic interferometer operating in the frequency range 1.05–1.44 MHz. Measurements have been made over the temperature range 145–240°K, and at pressures up to 680 atm. The results show good agreement with published data for pressures below 68 atm. Measurements at the critical temperature, 209.4°K, and at several nearby temperatures, provide information about the form of W–P–T and W–V–T surfaces near the critical point. Smoothed values of W have been used, together with published P–V–T data, to derive adiabatic compressibilities and constant‐pressure and constant‐volume specific heats for liquid krypton. The calculated specific heats, which have an estimated accuracy of 5%, show good agreement with the calorimetric measurements of Gladun and Menzel for the saturated liquid. However, our results suggest that Cv for liquid krypton is not independent of temperature in the ...

An experimental study of the equation of state of liquid mixtures of neon + normal hydrogen

Molar volumes of liquid mixtures of neon and normal hydrogen have been measured over the temperature range 25 to 31 K, and at pressures up to 34 atm. The experimental results have been used to derive the following properties: isothermal compressibility; heat capacity ratio ( C p / C v ); excess volume; and liquid density in the two-liquid region. Significant departures from ideal-mixing behavior are observed.

Phase Behavior of Light Gas Mixtures at High Pressures

If solid surfaces exist beneath the visible clouds of the major planets, they may be expected to exist at depths and pressures at which the component gas mixtures solidify under their own weight. The elucidation of phase behavior in mixtures of light gases at very high pressures is therefore essential to the solution of the problem of deep atmosphere structures in these planets. Available experimental evidence suggests several possible extrapolations of the H2-He phase diagram to high pressures. These have been used to develop a structural model for a H2-He atmosphere. In this model, gravitational separation of coexisting phases results in a layered structure, and it is shown that masses of H2-rich solid can exist in dynamic and thermodynamic equilibrium with a fluid layer of equal density but higher He content. This model forms the basis of a new hypothesis for Jupiter’s Red Spot.