Stochastic resolution of identity to CC2 for large systems: ground-state properties

TL;DR

This paper introduces a stochastic resolution of identity method for the CC2 model, significantly reducing computational costs for large systems while maintaining accuracy in ground-state energy calculations.

Contribution

The paper presents a stochastic approach to CC2 that reduces computational scaling from O(N^5) to O(N^3), enabling efficient large-system calculations.

Findings

Achieves accurate ground-state energies comparable to RI-CC2

Reduces computational scaling to O(N^3)

Demonstrates broad applicability across systems

Abstract

A stochastic resolution of identity approach (sRI) is applied to the second-order coupled cluster singles and doubles (CC2) model to calculate the ground-state energy. Utilizing a set of stochastic orbitals to optimize the expensive tensor contraction steps in CC2, we greatly reduce the overall computational cost. Compared with the RI-CC2 model, the sRI-CC2 achieves scaling reduction from O(N^5) to O(N^3), where N is a measure for the system size. When applying the sRI-CC2 to a series of hydrogen dimer chains, we demonstrate that the sRI-CC2 accurately reproduces RI-CC2 results for the correlation energies and exhibits a scaling of O(NH^2.71), with NH being the number of hydrogen atoms. Our calculations with different systems and basis sets show small changes in standard deviations, which indicates a broad applicability of our approach to various systems.