Auxiliary basis sets for density-fitting second-order Møller-Plesset perturbation theory: weighted core-valence...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Accurate calculations of electron correlation are crucial for understanding chemical properties.
• Standard basis sets can introduce significant errors, especially for heavy elements.
• Density fitting and explicitly correlated methods are computationally intensive but improve accuracy.

Purpose of the Study:

• Develop and optimize auxiliary basis sets (ABS) for 4d elements (Y-Pd).
• Evaluate the performance of these ABS in density fitting and explicitly correlated calculations.
• Assess the accuracy and convergence of spectroscopic constants for 4d monofluorides.

Main Methods:

• Development and optimization of auxiliary basis sets (ABS) matched to cc-pwCVnZ-PP and aug-cc-pwCVnZ-PP orbital basis sets (OBS).
• Second-order Møller-Plesset perturbation theory (MP2) calculations for core-valence electron correlation energies.
• Explicitly correlated coupled cluster calculations, including singles, doubles, and perturbative triples (CC(2,3)).
• Investigation of i-type functions in the resolution-of-the-identity component.

Main Results:

• New ABS significantly reduce errors in density fitting for 4d elements, making them negligible compared to OBS incompleteness.
• i-type functions are essential for controlling errors in integrals and correlation energy within explicitly correlated calculations.
• Explicitly correlated calculations with ABS show rapid convergence for spectroscopic constants of 4d monofluorides.
• Double-ζ calculations with ABS approach the accuracy of conventional quadruple-ζ, and triple-ζ achieves chemical accuracy.

Conclusions:

• The developed auxiliary basis sets provide a significant improvement in accuracy for 4d elements.
• These ABS are highly effective in reducing errors associated with density fitting and explicitly correlated methods.
• The findings enable more reliable and efficient quantum chemical calculations for transition metal systems.