Abstract
This research investigates molecular parameters such as equilibrium structure, dipole moment, rotational constant, harmonic frequency, adiabatic electron affinity, atomisation energy, and ionisation potential of some identified diatomic molecules in interstellar/ circumstellar medium. A theoretical understanding of the molecular properties of the investigated molecules is obtained using the popular B3LYP hybrid density functional with four basis sets: 6- 311++ G(2df, 2pd), 6- 311++ G(3df, 3pd), cc- pVTZ, and aug- cc- pVTZ. The computed data conform very well with available experimental and theoretical results. The accuracy of the B3LYP functional on the studied molecular systems are +/- 0.006 angstrom for the bond length, +/- 0.044 D for the dipole moment, +/- 0.854 GHz for the rotational constant, +/- 59 cm(-1) for the harmonic frequency, +/- 2.03 kcal/mol for the electron affinity, +/- 4.74 kcal/mol for atomisation energy, and +/- 3.19 kcal/mol for ionisation potential.