Explicitly correlated atomic orbital basis second order Møller-Plesset theory.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Ab initio wavefunction methods are expanding their scope with local approximations.
• Atomic orbital (AO) based methods exploit sparsity for large biomolecule calculations.
• Correlated wavefunction methods suffer from slow convergence and basis set incompleteness error (BSIE).

Purpose of the Study:

• To develop an atomic orbital (AO) based formulation of explicitly correlated MP2-F12 theory.
• To address the limitations of basis set incompleteness error (BSIE) in large-scale quantum chemical calculations.
• To enable more efficient and accurate quantum mechanical simulations of large molecular systems.

Main Methods:

• Formulation of an atomic orbital (AO) based explicitly correlated second-order Møller-Plesset perturbation theory (MP2-F12) method.
• Derivation of working equations for the AO-MP2-F12 method.
• Comparison of results with the established molecular orbital (MO) version of MP2-F12.

Main Results:

• The new AO-based MP2-F12 method produces results identical to the MO-based MP2-F12.
• The method avoids the need for a delocalized molecular orbital (MO) basis.
• Demonstrated applicability to noble gas dimers and linear alkane chains.

Conclusions:

• AO-based MP2-F12 offers a viable approach to reduce BSIE in quantum chemistry.
• The method paves the way for efficient, linear-scaling implementations.
• Future work includes a priori screening of contraction terms and further optimization for large systems.