First principles multielectron mixed quantum/classical simulations in the condensed phase. I. An efficient...

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Materials Science

Background:

• Accurate electronic structure calculations are crucial for understanding chemical and physical phenomena.
• Existing methods often struggle with computational cost for large systems or complex electron correlation effects.
• Mixed quantum/classical simulations require efficient electronic structure methods capable of handling condensed-phase environments.

Purpose of the Study:

• To introduce and validate the two-electron Fourier-grid (2EFG) method for first-principles electronic structure calculations.
• To demonstrate the efficiency and accuracy of the 2EFG approach in mixed quantum/classical simulations.
• To provide a computationally feasible method for treating electron correlation and exchange exactly.

Main Methods:

• Developed the two-electron Fourier-grid (2EFG) approach, solving the six-dimensional two-electron Schrödinger equation.
• Utilized a Fourier-grid representation for efficient parallelization and computation.
• Implemented the method in a distributed-memory parallel environment.
• Benchmarked accuracy using the harmonium atom and sodium dimer.

Main Results:

• The 2EFG method achieves high efficiency, calculating two-electron wave functions in approximately 20 seconds.
• It accurately reproduces exact solutions for the harmonium atom across different correlation regimes.
• The method shows comparable accuracy to valence CI for sodium dimer potential energy curves.
• Demonstrated applicability to molecular systems and potential for condensed-phase simulations.

Conclusions:

• The 2EFG method is a highly efficient and accurate first-principles electronic structure technique.
• It is well-suited for mixed quantum/classical simulations of condensed-phase systems.
• The method's exact treatment of electron correlation and exchange opens new possibilities for complex chemical problems.