Understanding discrepancies in noncovalent interaction energies from wavefunction theories for large molecules

Area of Science:

• Quantum chemistry
• Computational physics
• Molecular modeling

Background:

• Accurate calculation of molecular interactions is vital for understanding chemical processes.
• Current reference methods for solving the many-electron Schrödinger equation face challenges with large, complex molecules.

Purpose of the Study:

• To investigate discrepancies in noncovalent interaction energies predicted by diffusion quantum Monte Carlo and coupled-cluster theory.
• To identify the primary source of these discrepancies in large molecular systems.

Main Methods:

• Comparison of diffusion quantum Monte Carlo and coupled-cluster theory results.
• Analysis of noncovalent interaction energies for large molecules (hundred-atom scale).

Main Results:

• Unequivocal identification of the main source of puzzling discrepancies between the two theories.
• Development of modifications to widely-used coupled-cluster methods.

Conclusions:

• Modified coupled-cluster methods provide more accurate noncovalent interaction energies for large, polarizable molecules.
• Enhanced accuracy impacts a wide range of applications relying on intermolecular interactions.