The simplest models in thermodynamics of low concentrated binary liquid
alloys
L. A. Bolshov, V.I. Bogdanov, V.A.Gorbunov
Faculty of Electroenergy, State technical university of Vologda,
160000, Vologda, 15 Lenin’s street, Russia
E-mail: vagor@mh.vstu.edu.ru
Rigorous from the point of view of statistical mechanics and a quantum theory approaches to
thermodynamics of liquid alloys encounter extreme difficulties. Therefore attempts to consider
thermodynamic properties of liquid alloys within the framework of the lattice model of solution still are
of great heuristic importance. The logarithm of the rational activity coefficient of an impurity in a binary
solution and partial excess enthalpy of an impurity can be expanded into the series on degrees of
concentration. Alloys for which these expansions converge, we call low concentrated. The coefficient in
the linear term of expansion of the logarithm of an activity coefficient is called Wagner interaction
coefficient. The coefficient in the linear term of expansion of a partial excess enthalpy is called first order
interaction coefficient. The theory for Wagner interaction coefficient and first order enthalpy coefficient
in binary liquid alloys within the framework of the lattice model of a solution and Hamiltonian of Izing
type is considered. The radius of interatomic interaction is supposed any arbitrary. In this model values of
enthalpy coefficients in general can not be expressed through values of Wagner interaction coefficients.
In our paper two limiting cases when these coefficients appear connected with each other by simple
formulas are singled out. These formulas coincide with those following from the theory of regular
solutions and quasichemical theory. It is stated that the first of these formulas is in agreement with
experimental data approximately for 30 % of the examined systems, the second formula is only for rather
restricted number of systems.