J. Amorós

Equations of state for hard spheres fluid in the metastable fluid region

A number of existing approximants are reviewed and tested for the equation of state of the hard spheres fluid in the metastable fluid region, namely, at densities higher than the normal freezing density: ρ*=0.943. This is a region which is particularly sensitive to the quality of a given equation of state; however, it is frequently ignored in the study of analytical equations of state. A new set of approximants is also discussed, including as particular cases several other currently used equations of state for the hard spheres fluid.

Behaviour of the internal pressure of liquids in accordance with variations in temperature, volume and cohesive energy density

Abstract A study is made of the variations to be found in the internal pressure of different types of liquid in accordance with variations in temperature and volume. These relationships are established through simple analytical equations. Variations in the cohesive energy density and the Hildebrand parameter in accordance with temperature variations are also calculated and it is shown that the internal pressure and the cohesive energy density are both analogous manifestations of the cohesion property of liquids and of the diminution of this property with falls in temperature.

Equations of state for D-dimensional hard sphere fluids

Abstract An equation of state, a kind of generalized Pade approximant, first proposed for the hard-sphere fluid in three dimensions is extended to the two-, four-, and five-dimensional cases in addition to the trivial one-dimensional case (hard rods). The corresponding equations of state show good to excellent agreement with existing simulation data.

Predicting the translational-rotational coupling factor for polyatomic molecules from the self-diffusion coefficient

The translational-rotational coupling factor, or roughness factor, introduced by Chandler, has been evaluated for twelve substances in the liquid range (between the triple and critical points) by means of a reduced number of self-diffusion data. The influence of experimental data, simulation procedures, different choices for the hard sphere diameter, and the introduction of the modified Enskog theory have been included in this study. The results support the validity of the model.

Equations of State for Four-and Five-Dimensional Hard Hypersphere Fluids

Abstract Equations of state for the four- and five-dimensional hard hypersphere fluids have been obtained. Several procedures have been considered in each case: a) adapting the method of Carnahan and Starling to such dimensionalities; b) introducing Pade and Levin approximants suitable to the virial expansion and c) establishing a pole at a given density. In most cases, the results obtained agree satisfactorily with the available simulation data. The use of an additional fitting parameter furnishes nearly perfect agreement.

Equations of state for non-spherical hard-particle fluids

Abstract A new type of approximant, previously proposed for the equation of state of the hard-sphere fluid, is applied to obtain equations of state of non-spherical hard-particle fluids. For prolate and oblate spherocylinders, prolate and oblate ellipsoids of revolution, homonuclear and heteronuclear diatomics, the known virial coefficients are fitted as polynomials in the shape factor α and then the approximants are constructed from the fittings. The equations of state thus obtained are in very good agreement with existing simulation data.

More accurate equations of state for non-spherical hard-particle fluids

Equations of state for several non-spherical hard-particle fluids (prolate and oblate spherocylinders, prolate and oblate ellipsoids of revolution, homonuclear and heteronuclear diatomics) are developed for several geometrical shapes. For each type of particle, the known virial coefficients are fitted as polynomials in the shape factor α and then approximants, of a new type previously proposed for the hard sphere fluid, are constructed from the fittings. The equations of state thus obtained are in good to excellent agreement with existing simulation data and constitute a great improvement on other equations of state currently used for these fluids.

Correlation among several physicochemical properties of alkali metals in the light of the corresponding states principle

The objective of this work is to analyse several physicochemical properties (practically all equilibrium properties) for alkali metals (Li, Na, K, Rb and Cs) from the corresponding states principle along the liquid–vapour coexistence line. Selecting the best experimental data, we plot the reduced quantities versus reduced temperature. In all cases, the behaviour of these substances is well correlated. For K, Rb and Cs, a common line adequately represents such behaviour. From the results, we conclude the validity of this principle in the context.

A test of the modified Enskog theory for the transport properties of liquids

The modified Enskog theory (MET) has been applied to various fluids in the liquid range (between the triple point and the critical point), and the viscosity, thermal conductivity, and self-diffusion coefficients have been calculated. The temperature dependence of the covolume has been introduced explicitly, bypassing the use of virial coefficients. The agreement is generally acceptable and sometimes good. There is an evident regularity in the results when the reduced temperature is introduced as an independent variable.

Prediction methods for the critical temperature of n-alkanes

The critical temperature of heavy n -alkanes is predicted from the behaviour corresponding to their melting temperature and from several empirical correlations. The prediction methods for the critical temperature of n -alkanes are reviewed, including the new experimental data currently available. The results obtained for