Theoretical models for the thermodynamic properties of linear triatomic molecules

Using the improved Manning-Rosen and harmonic oscillator potentials to model the symmetric, asymmetric, and degenerate bending vibrational modes in linear triatomic molecules, equations are developed to assess enthalpy, Gibbs free energy, isobaric heat capacity, and entropy based on the partition function of the system. These formulations are applied to evaluate the thermodynamic properties of linear triatomic molecules such as BeF₂, CNC, COS, and MgCl₂. The models yield average percentage absolute deviations (APAD) of less than 1 % when compared to experimental data for most molecules. The data are consistent with existing literature on triatomic molecules.