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

In this paper, we have derived an equation of state (EoS) for liquid alkali metals based on a suggested potential function over the whole liquid range including metal–nonmetal transition. This EoS is based on the interaction of nearest neighbors according to the characteristics of the soft repulsive interaction in dense and large attractive interaction in expanded liquid alkali metals. PVT data of dense liquid alkali metals obey the equation (2Z − 1)Vm = A + Bρ over the whole range of liquid densities, where Z, Vm, and ρ are compression factor, molar volume, and molar density, respectively. The intercept A and slope B of this equation are related to the attractive and repulsive parts of suggested potential function, respectively, and both depend on temperature. The new EoS has been used to calculate the molar density and other thermodynamic properties such as isobaric expansion coefficient, αP; isothermal compressibility, κT; and internal pressure, Pi; of liquid alkali metals at any temperature and pressure over the whole liquid range. The results show good agreement between the values obtained using this equation and the experimental and literature data. To show the ability of this EoS in prediction of thermodynamic properties of liquid alkali metals over the whole liquid range, the results have been compared with some other equations.

► A new equation of state has been suggested for alkali metals over whole liquid range.
► Liquid density and other thermodynamic properties of alkali metals are calculated.
► A wide comparison between this equation and some previous works has been made.