Bond-equilibrium theory of liquid Se-Te alloys. II. Effect of singly attached ring molecules

Abstract

A statistical-mechanical theory for bond equilibrium of chain polymers containing threefold (3F) and onefold (1F) bond defects is extended to include the effects of free ring molecules and ring molecules attached to chains by a single 3F atom. Positively charged singly attached rings are shown to play a key role in bond equilibrium in liquid ${\mathrm{Se}}_x$ ${\mathrm{Te}}_{1-x}$ by permitting the formation of ion pairs in which both constituents are effectively chain terminators, thus decreasing the average polymer size. The theory is applied to explain the behavior of the paramagnetic susceptibility, ${\chi }_p$, and electronic transport as affected by the Fermi energy $E_F$. It is found that the increase in ${\chi }_p$ with the concentration of Te is primarily the result of the smaller energy for breaking Te bonds. In addition, attached rings play an important role in determining the effect of temperature on ${\chi }_p$. At $x\lesssim 0.5$, the concentrations of both free and attached rings becomes small at high $T$ because of the high concentration of bond defects.