On the thermodynamic consequences of the threefold isomerism in the LiCN system

The LiCN system which was recently characterized computationally, is considered to be an equilibrium mixture of three isomeric species (lithium isocyanide, a bridged species and lithium cyanide). While the isocyanide prevails at low temperatures, at moderate and higher temperatures the isocyanide and bridged species can exhibit comparable stability or even stability interchange. The overall standard heat capacity at constant pressure shows a clear temperature maximum; the isomeric enhancement of heat capacity can be as high as 19.5 J K^-1 mol^-1. The role of structural fluxionality is discussed briefly.