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Efficient Computation of Two-Electron Reduced Density Matrices via Selected Configuration Interaction.

Jeremy P Coe¹, Andrés Moreno Carrascosa², Mats Simmermacher²

¹Institute of Chemical Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, EdinburghEH14 4AS, U.K.

Journal of Chemical Theory and Computation

|October 5, 2022

Summary

This summary is machine-generated.

We developed an efficient method to calculate two-electron reduced density matrices (2-RDMs) using selected configuration interaction wavefunctions. This approach, demonstrated with Monte Carlo configuration interaction (MCCI), offers accurate results with fewer computational resources.

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Area of Science:

Quantum chemistry
Computational physics

Background:

Calculating two-electron reduced density matrices (2-RDMs) is crucial for understanding molecular properties.
Accurate computation of 2-RDMs often requires significant computational resources, especially for complex systems.

Purpose of the Study:

To develop an efficient computational approach for calculating 2-RDMs.
To enable accurate comparisons between different selected configuration interaction methods and full configuration interaction (FCI).

Main Methods:

Utilizing selected configuration interaction wavefunctions, specifically Monte Carlo configuration interaction (MCCI).
Accelerating 2-RDM computation using fast full configuration interaction (FCI) implementation strategies.
Employing hardware bitwise operations for efficient Slater-Condon rule implementation.

Main Results:

The developed method allows for efficient and accurate calculation of 2-RDMs for various molecular systems, including those with stretched bonds and excited states.
The accuracy of energies, wavefunctions, and 2-RDMs obtained via MCCI and truncated CI methods shows similar trends when compared to FCI.
MCCI demonstrates the ability to achieve high 2-RDM accuracy with a substantially lower number of configurations compared to truncated CI, particularly for multireference systems.

Conclusions:

The novel approach provides an efficient pathway for accurate 2-RDM calculations in quantum chemistry.
MCCI emerges as a computationally advantageous method for obtaining accurate 2-RDMs, especially for challenging systems with strong multireference character.