Gas-phase and solid-state electronic structure analysis and DFT benchmarking of HfCO

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Understanding the electronic structure and bonding of transition metal compounds is crucial for catalysis and materials design.
• Hafnium carbonyl (HfCO) and its analogs represent an interesting class of molecules with potential applications.
• Accurate theoretical methods are needed to predict the properties of these systems.

Purpose of the Study:

• To computationally investigate the ground and excited electronic states of HfCO.
• To determine key molecular properties including potential energy curves, dissociation energies (De), excitation energies, and vibrational frequencies.
• To evaluate the accuracy of various Density Functional Theory (DFT) functionals for describing HfCO and its interaction with a Hf surface.

Main Methods:

• Employed ab initio multi-reference configuration interaction (MRCI) and coupled cluster singles doubles and perturbative triples [CCSD(T)] methods for high-accuracy electronic structure calculations.
• Analyzed potential energy curves, dissociation energies, excitation energies, and harmonic vibrational frequencies.
• Assessed 23 DFT exchange-correlation functionals against CCSD(T) benchmarks for gas-phase HfCO and Hf surface chemisorption.

Main Results:

• The ³Σ^- ground state of HfCO exhibits a dissociation energy (De) of approximately 30 kcal mol^-1.
• A linear relationship was observed between the De of isovalent HfCX (X = S, Se, Te, Po) series and the dipole moment of the CX ligand, also seen for TiCX and ZrCX.
• Global GGA hybrid B3LYP and range-separated hybrid ωB97X functionals showed good performance for HfCO ground state properties (De and ionization energy).

Conclusions:

• The study provides accurate computational data for HfCO electronic states and bonding.
• Identified predictable trends in dissociation energies across isovalent HfCX, TiCX, and ZrCX series.
• Surface chemisorption energies of CO on Hf surfaces show moderate transferability from gas-phase molecular benchmarks depending on the DFA used.