Pushing configuration-interaction to the limit: Towards massively parallel MCSCF calculations

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Accurate electronic structure calculations are crucial for understanding molecular properties.
• Large active space calculations are computationally demanding and limit scientific inquiry.
• Existing methods struggle with the scale required for complex systems.

Purpose of the Study:

• To develop and present a scalable parallel implementation of multiconfigurational self-consistent field (MCSCF) methods.
• To enable large-scale configuration interaction (CI) calculations within the NWChem code.
• To push the boundaries of computational chemistry for complex molecular systems.

Main Methods:

• Implementation of a generalized active space approach for partitioning configuration interaction vectors.
• Development of a massively parallel MCSCF algorithm for distributed computing.
• Utilizing the open-source NWChem computational chemistry code.

Main Results:

• Successful execution of large-scale parallel MCSCF calculations.
• Routine performance of calculations with 20 electrons in 20 orbitals for systems like chromium trimer.
• Achieved unprecedented CI calculations for pentacene (22 electrons in 22 orbitals) and chromium tetramer (24 electrons in 24 orbitals).

Conclusions:

• The new parallel MCSCF implementation significantly enhances the capability for large-scale electronic structure studies.
• This work represents the largest conventional configuration interaction calculation to date.
• The developed methods open new avenues for investigating complex quantum mechanical systems.