Effect of branched chain polymers on bond equilibrium in liquid Se-Te alloys

Abstract

The statistical-mechanical method for deriving the usual expression for the law of mass action (LMA) is modified by replacing the configuration entropy $S_c$ of an ideal solution with an expression which reflects the polymeric structure. A quasilattice model is used to determine $S_c$, using an extension of a method due to Flory. The present work ignores the effects of ring molecules, which may play an important role in real alloys. The derived expressions for the concentrations of neutral or electrically charged dangling bond ($1F$) and threefold bonded ($3F$) atoms are modified from the LMA results by factors whose values depend on the total concentrations of $1F$ and $3F$ atoms. They reflect the entropies of formations $s_1$ and $s_3$ of $1F$ and $3F$ constituents which are functions of the average number $\lambda$ of chain branches per molecule. When $\lambda$ is large $s_1\simeq -s_3\simeq k\ln \lambda$. The effects of alloying are essentially independent of the polymer effect, and are the same as what is predicted by LMA.