Modified Scarf-type interaction potential for vibrational energy eigenvalues and chemical equilibrium constants of selected diatomic molecules

Abstract Accurate interaction potentials play an important role in the determination of vibrational, thermodynamic, and chemical equilibrium properties of diatomic molecules. In this work, a modified Scarf-type (MST) interaction potential is proposed and applied to the determination of vibrational energy eigenvalues and chemical equilibrium constants. An explicit expression for the vibrational energy eigenvalues is obtained from the radial Schrödinger equation using the parametric Nikiforov-Uvarov method. The resulting energy spectrum is subsequently employed in the determination of thermodynamic and chemical equilibrium properties. Validation against experimental and reference data demonstrates the reliability of the proposed model. Comparisons with Rydberg-Klein-Rees data and experimental vibrational energies for Br 2 , PO, and SO yield MPAD values below 3%, indicating good agreement between theory and experiment. Comparisons with NIST-JANAF thermochemical data further reveal close agreement for the chemical equilibrium constants of BrF, NO, PO, and SO, with MPAD values below 2% for BrF and NO and similarly favorable agreement for PO and SO at moderate and high temperatures. These findings establish the MST interaction potential as a useful framework for molecular spectroscopy, thermodynamic modeling, and chemical equilibrium studies of diatomic molecules.