Quantum Monte Carlo Methods Describe Noncovalent Interactions with Subchemical Accuracy

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Molecular Interactions

Background:

• Accurately describing noncovalent interaction energies is crucial but challenging in computational chemistry.
• Current benchmark methods like coupled cluster singles and doubles with perturbative triples (CCSD(T))/complete basis set (CBS) are computationally expensive for complex systems.

Purpose of the Study:

• To evaluate the fixed-node diffusion Monte Carlo (FN-DMC) method for calculating noncovalent interaction energies.
• To determine if FN-DMC can achieve benchmark accuracy with a more favorable computational scaling.

Main Methods:

• Utilized the fixed-node diffusion Monte Carlo (FN-DMC) method.
• Tested FN-DMC on a set of six small noncovalent complexes, including the water dimer.
• Compared FN-DMC results against established CCSD(T)/CBS benchmark calculations.

Main Results:

• FN-DMC achieved accuracy within subchemical limits (<0.1 kcal/mol) compared to CCSD(T)/CBS.
• For benzene/water, benzene/methane, and T-shape benzene dimer, FN-DMC results agreed within 0.25 kcal/mol of CCSD(T)/CBS estimates.
• FN-DMC demonstrated favorable computational scaling compared to traditional methods.

Conclusions:

• FN-DMC is a viable and accurate method for calculating noncovalent interaction energies.
• Its efficiency and accuracy open new avenues for studying larger and more complex noncovalent systems.
• This method offers a powerful alternative to computationally demanding benchmark calculations.