Benchmarking the Quantum Chemical Methods to Examine Ground and Excited States Electronic Structure of Diatomic Molecules

The predictive ability of various quantum chemistry based ab initio methods were examined for the ground and excited states electronic structure of highly functional diatomic molecules, formed by the elements of groups XV, XVI, and XVII of the periodic table. The bond length and dissociation energy of these diatomic molecules in their singlet and triplet states as well as their optical absorption spectra are obtained for benchmarking. Our study reveals that out of the methods examined, namely, HF, SCI, SDCI, MRSDCI, QCI, CCSD, and TD-DFT, none of them cannot be universally employed to accurately predict the above properties of these molecules. However, through a comprehensive analysis we proposed the suitability each of these methods for individual properties of individual molecules. The present study reveals new optical absorption peaks within the ionization limit for N₂, S₂, and I₂. The affirmation objectives are significant because of the rapidly growing interest in the functionalization of molecules on the solid surface and 2d materials.