Electronic Structure of Diatomic Nickel Sulfide

Area of Science:

• Computational Chemistry
• Materials Science
• Surface Chemistry

Background:

• The nickel-sulfur (Ni-S) bond is critical for understanding the adsorption of atmospheric Lewis acid gases, including sulfur dioxide (SO2) and sulfur trioxide (SO3), onto nickel surfaces.
• Accurate theoretical prediction of Ni-S bond properties is essential for developing materials with tailored gas adsorption capabilities.

Purpose of the Study:

• To investigate the electronic structure and vibrational frequency of the Ni-S bond using high-level quantum chemical methods.
• To benchmark various density functional theory (DFT) functionals for their accuracy in predicting Ni-S bond properties.
• To assess the applicability of DFT methods for modeling reactions involving Ni-S species in acid gas adsorption systems.

Main Methods:

• High-level quantum chemical calculations, including Coupled Cluster Singles Doubles and Triples (CCSD(T)), Complete Active Space Self-Consistent Field (CASSCF), and internally contracted Multireference Configuration Interaction (icMRCI) + Q.
• Benchmarking of 43 different DFT functionals against established theoretical methods and experimental data.
• Calculation of vibrational frequencies, ground state electronic configurations, and bond dissociation energies for NiS.

Main Results:

• The ground state of NiS was determined to be the 3Σ− state at the icMRCI + Q level, consistent with experimental findings, correcting the CASSCF prediction of a 5Δ state.
• The calculated vibrational frequency of Ni-S (519.1 cm−1) using icMRCI + Q showed good agreement with the experimental value (512.68 cm−1).
• BP86 and O3LYP were identified as the most accurate DFT functionals for predicting the Ni-S vibrational frequency among the 43 tested. DFT methods showed variable accuracy in predicting the energy for NiO displacement by SO.

Conclusions:

• High-level quantum chemical methods, particularly icMRCI + Q, provide accurate predictions for the Ni-S bond properties, including its ground state and vibrational frequency.
• DFT methods, specifically BP86 and O3LYP, show promise for modeling Ni-S interactions relevant to acid gas adsorption, although their performance can vary depending on the specific reaction.
• The study validates the use of computational methods for understanding Ni-S bonding and its role in surface interactions with atmospheric pollutants.