Linear Exp-6 Isotherm for Compressed Molten Cesium over the Whole Liquid Range Including Metal−Nonmetal Transition and T_c

Abstract

The linear exp-6 isotherm is presented as an approach to the thermodynamic properties of liquid alkali metals over the whole liquid range including metal-nonmetal transition. The exp-6 pair interaction potential is applied to approach the underlying interplay between the characteristics soft repulsive interaction in dense, large attractive interaction in expanded liquid alkali metal and the observed thermodynamic properties. PVT of dense liquid alkali metals obey the linear exp-6 isotherm (Z -1)V 2 ) A + BF -7/3 exp[R(1 -CF -1/3 /r m ) over the whole range of liquid densities, where Z is the compression factor, F ) 1/V is the density, r m is the position of potential minimum, R is a parameter, and C is a constant. The intercept A and the slope B significantly are related to attraction and repulsion, respectively, and both depend on temperature. At the level of theory presented in this study, the thermodynamic effects caused by the polarization of atoms in expanded liquid alkali metals can be accounted for by exp-6 potential function to demonstrate their thermodynamic properties as normal liquids. This includes the metal-nonmetal's transition range in which case the nature of forces is changed in such a way that the thermodynamic properties would be different from those of the high-density region. In particular, the equation of state for molten cesium is analytical over the whole range of liquid densities. The linear exp-6 isotherm is used to estimate the binding energy (0.0733 eV) and the position of potential minimum (5.336 Å) of liquid cesium at freezing temperature.

A new equation of state for molten alkali metal alloys

“…The variations of ε and r m with temperature for liquid metals and normal fluids have been already investigated [32][33][34][35][36][37]. The values of r m calculated from Eq.…”

“…The values of r m calculated from Eq. (10) and those obtained from X-ray diffraction measurements and also literature data [33,34,38] for cesium, potassium, and sodium at their melting temperatures have been given in Table 1. As this table shows, the predicted values are quite close to the literature data.…”

“…1 on which up to 1350 K, r m increases linearly with temperature and bends upward thereafter. According to the literature [32][33][34], there is a change in the cesium structure after 1350 K, the temperature on which the metal-nonmetal transition occurs. Fig.…”

Density prediction of liquid alkali metals and their mixtures using an artificial neural network method over the whole liquid range

“…During the last decades, many studies have been devoted to prediction of thermodynamic properties of liquid alkali metals [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24], and their alloys [25][26][27][28][29]. Different authors used different equations and methods to predict and reproduce the thermodynamic properties of these systems.…”

A new regularity and an equation of state for alkali metals over the whole liquid range

“…Liquid alkali metals have been studied widely during the last decades by several researchers [10][11][12][13][14][15][16][17][18][19][20][21]. In a recent study, the GMA (Goharshadi-Morsali-Abbaspour) EoS has been applied to molten alkali metals in a narrow range of temperatures and pressures [19].…”