LINEAR VERSUS CYCLIC (HCN)3 - A COMPUTATIONAL THERMODYNAMIC STUDY

The trimer of HCN is treated as an equilibrium mixture of two species, linear and cyclic, using a partition-function treatment supplied with recent computed parameters. The linear isomer, which is favoured in potential energy by about 3 kJ mol-1, is always the prevailing structure. The highest inter-isomeric coexistency degree is reached at about 630 K when the linear form represents 91% of the equilibrium mixture. Isomerism contributions to enthalpy, entropy and heat capacity exhibit an interesting temperature course with a maximum. Several exact thermodynamic inter-relations are demonstrated on the system.