Nuclear Quantum Effects Made Accessible: Local Density Fitting in Multicomponent Methods.

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Materials Science
• Biophysics

Background:

• Nuclear quantum effects (NQEs) are essential for accurately describing systems with light nuclei, particularly hydrogen.
• The implications of NQEs span chemistry, biology, physics, and materials science, yet computationally accessible methods remain limited.
• Current electronic structure theory methods are routine, but lack efficient approaches for incorporating NQEs.

Purpose of the Study:

• To develop a computationally efficient and accessible method for simulating nuclear quantum effects (NQEs).
• To integrate the nuclear-electronic orbital Hartree-Fock (NEO-HF) approach with local and density fitting approximations (LDF).
• To enable the inclusion of NQEs in large-scale systems relevant to various scientific disciplines.

Main Methods:

• Introduced the local and density fitting approximations to the nuclear-electronic orbital Hartree-Fock (LDF-NEO-HF) method.
• Developed a low-order scaling computational approach for simulating NQEs.
• Applied the LDF-NEO-HF method to chemical, biological, and materials science use cases.

Main Results:

• Achieved a low-order scaling approach for including NQEs, significantly reducing computational cost.
• Enabled NQE simulations for large systems in under a day and for smaller systems in minutes.
• Demonstrated the qualitative accuracy and robustness of the LDF-NEO-HF approach across diverse applications.

Conclusions:

• The LDF-NEO-HF method provides an efficient and accessible means to incorporate NQEs in quantum chemical calculations.
• This approach facilitates the study of systems where NQEs play a critical role, advancing multiple scientific fields.
• The developed method represents a significant step forward in computational modeling for complex chemical, biological, and material systems.