Accurate thermochemistry for transition metal oxide clusters

Area of Science:

• Computational Chemistry
• Materials Science
• Quantum Chemistry

Background:

• Transition metal oxide clusters are crucial in catalysis and materials science.
• Accurate calculation of their thermodynamic properties is essential for understanding their behavior.
• Previous studies often faced challenges with basis set dependency in calculations.

Purpose of the Study:

• To develop an efficient strategy for calculating accurate thermodynamic properties of transition metal oxide clusters.
• To investigate the basis set dependency of total atomization energies (TAEs) and normalized clustering energies (NCEs).
• To benchmark the performance of various density functional theory (DFT) functionals for these calculations.

Main Methods:

• Coupled cluster [CCSD(T)] and density functional theory (DFT) calculations were employed.
• Calculations were performed for group IVB (Ti, Zr, Hf) and VIB (Cr, Mo, W) oxide clusters up to n=4.
• An efficient strategy was developed using cluster unit properties and NCEs.

Main Results:

• TAEs were highly basis set dependent, while NCEs were significantly less so.
• Calculated TAEs, NCEs, and heats of formation were compared with experimental data.
• The PBE1PBE hybrid functional showed the best performance for NCE calculations, with small deviations for dimers, trimers, and tetramers.

Conclusions:

• The developed strategy provides an efficient route to accurate thermodynamic properties of large clusters.
• Hybrid DFT functionals generally outperform pure functionals for NCE calculations.
• DFT functional performance for TAEs depends on the electronic state of the transition metal atom, with performance degrading with increasing cluster size.