Accurate thermochemistry for transition metal complexes from first-principles calculations

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Accurate prediction of molecular thermodynamics is crucial for chemical research.
• Existing ab initio methods face challenges with transition metal systems.
• The need for a reliable and accurate computational approach for diverse chemical species.

Purpose of the Study:

• To introduce and validate the "correlation consistent Composite Approach" (ccCA) for thermochemical predictions.
• To assess the accuracy of ccCA for both main group and transition metal-containing molecules.
• To establish ccCA as a robust tool for quantitative theoretical modeling.

Main Methods:

• Utilizing an ab initio model chemistry based on the single reference MP2 level of theory.
• Adjusting basis set and level of theory for core valence additive correction.
• Employing the G2/97 test set for benchmarking main group species.

Main Results:

• ccCA achieved a mean absolute deviation of 0.89 kcal mol(-1) for 147 enthalpies of formation in the G2/97 test set.
• For transition metal complexes (Sc-Zn), ccCA predicted enthalpies of formation within +/-3 kcal mol(-1) of experimental results.
• Demonstrated mean absolute deviation of 2.85 kcal mol(-1) and root mean square deviation of 3.77 kcal mol(-1) for transition metal systems.

Conclusions:

• The ccCA methodology provides reliable thermochemical predictions for a wide range of molecules.
• ccCA represents a significant advancement in the quantitative theoretical modeling of transition metal thermodynamics.
• The approach shows high accuracy, comparable to chemical accuracy standards.