On the Zero Wavenumber Structure Factors of Binary Associating Mixtures

Abstract

By equating the appropriate scattering expressions, the structure factors (SF) S_CC (0), S_NC (0) and S_NN (0) of a binary A-B alloy with tendency to form associates A_μB_ν , (μ, ν small integers), are expressed in terms of the six SF S_αβ ¹ (0) of the ternary mixture of A, B and A_μB_ν and their concentrations x _α (α = 1, 2, 3). When x _α satisfy the equilibrium condition for the reaction μA + νB ⇌ A_μB_ν , these relations become thermodynamic identities; otherwise they determine S_CC (0) etc. for the nonequilibrium situations. The difference between S_CC (0) etc., when there is equilibrium and when the chemical degree of freedom is frozen in, say, by quenching, is discussed. The relations between the above S_CC (0) etc. and the corresponding SF for a strongly associating mixture in the “chemical” scheme (system regarded as a binary mixture of A_μB_ν and A or B atoms) are also obtained.