Nonempirical models for assessing thermal properties of nonlinear triatomic molecules of the form XY₂.

The current study explores computational models developed using the improved Scarf potential and harmonic oscillator to simulate vibrational modes in nonlinear polyatomic systems. These models are derived from the partition functions of the system and are designed to predict molar Gibbs free energy, entropy, enthalpy, and heat capacity. The models are applied to nonlinear polyatomic molecules, including aluminum chloride (AlCl2), boron difluoride (BF2), and sulfur dioxide (SO2). For Gibbs free energy and entropy, the equations yield a mean percentage relative error (MPRE) of no more than 0.09% compared to NIST-JANAF data. Furthermore, using the heat capacity expression, MPRE values of 0.968%, 1.035%, and 2.764% are obtained for AlCl2, BF2, and SO2, respectively. These findings are in good agreement with results from existing literature on nonlinear molecules.