Orbital-Optimized MP3 and MP2.5 with Density-Fitting and Cholesky Decomposition Approximations

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Orbital-optimized MPn methods (OMP3, OMP2.5) offer improvements over standard MPn methods.
• Computational cost remains a barrier for applying these advanced methods to larger systems.

Purpose of the Study:

• To present efficient implementations of density-fitting (DF) and Cholesky decomposition (CD) approaches for OMP3 and OMP2.5.
• To evaluate the computational cost reduction achieved by these new methods compared to conventional OMP3 and OMP2.5.
• To demonstrate the applicability of DF/CD-OMP3 and DF/CD-OMP2.5 to challenging molecular systems.

Main Methods:

• Implementation of density-fitting (DF) and Cholesky decomposition (CD) approximations for OMP3 and OMP2.5.
• Application of the developed DF/CD-OMP3 and DF/CD-OMP2.5 methods to a set of alkane molecules.
• Comparison of computational costs between DF/CD-OMP3/2.5 and conventional OMP3/2.5.

Main Results:

• DF-OMP3 and DF-OMP2.5 methods exhibit considerably lower computational costs than their conventional counterparts.
• The orbital-optimized methods are effective for studying open-shell noncovalent interactions.
• These methods accurately calculate aromatic bond dissociation energies and hydrogen transfer reactions.

Conclusions:

• DF-OMP3 and DF-OMP2.5 provide significant computational savings.
• Orbital-optimized methods are valuable tools for investigating complex electronic structures.
• The developed methods show great promise for future applications in computational chemistry.