The variational two-electron reduced density matrix (v2RDM) approach provides polynomially-scaling path to the description of strongly correlated electrons. This favorable scaling is achieved via the direct optimization the second-order reduced density matrix (RDM), as opposed to wave function parameters. While promising, the v2RDM approach exhibits a number of well-known deficiencies, and the precise origin of the errors in such calculations is not clear. It is, however, at least understood that low-order N-representability conditions (i.e., two-particle constraints on the RDMs) are insufficient for achieving quantitative accuracy. In this research, we applied the both two-particle and the full set of three- N-representability constraints to assess the accuracy of the approach for a series of strongly-correlated model systems. <b>It has been found that systems with larger 3-body cumulants are more challenging for v2RDM methods, though it is not the only factor.</b> Different geometry series exhibit different sensitivities towards the 3-body cumulants. Among the studied model systems, the number of applied constraints remains the most important accuracy determining factor.

Signatures of strong electron correlation from the three-electron cumulant reduced density matrix

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.