Error Control and Automatic Detection of Reference Active Spaces in Many-Body Expanded Full Configuration...

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Electronic Structure Theory

Background:

• The many-body expanded full configuration interaction (MBE-FCI) method offers a way to achieve highly accurate electronic structure calculations.
• Manual selection of active spaces in MBE-FCI can introduce bias and limit its applicability.
• Unfavorable computational scaling with the number of orbitals can hinder the efficiency of MBE-FCI.

Purpose of the Study:

• To present a comprehensive revamp of the generalized MBE-FCI method.
• To reduce bias in active space selection through automation.
• To improve the computational efficiency and applicability of MBE-FCI.

Main Methods:

• Automated selection of reference active spaces to minimize bias.
• Utilization of compact orbital clusters as expansion objects to circumvent unfavorable scaling.
• Development of a new algorithm for efficient termination of many-body expansions with error control.

Main Results:

• Demonstrated automated active space selection reducing inherent bias.
• Showcased improved computational scaling by using compact orbital clusters.
• Validated a new algorithm for efficient and error-controlled termination of many-body expansions.
• Successfully produced correlation energies within predetermined error bounds across various molecular systems and orbital representations.

Conclusions:

• The revamped MBE-FCI method significantly broadens the applicability of the approach.
• Automated active space selection and efficient expansion termination enhance accuracy and usability.
• The developed methods provide a robust framework for accurate electronic structure calculations.