English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We report the failure of coupled-cluster valence-bond (CCVB) theory withtwo-pair configurations [J. Chem. Phys. 2009, 130, 084103 (2009)] foropen-shell (OS) spin-frustrated systems where including three-pairconfigurations is necessary to properly describe strong spin-correlations. Weextend OS-CCVB by augmenting the model with three-pair configurations withinthe independent amplitude approximation (IAA). The resulting new electronicstructure model, OS-CCVB+i3, involves only a quadratic number of independentwavefunction parameters. It includes the recently reported closed-shell CCVB+i3as a special case. Its cost is dominated by integral transformations and it iscapable of breaking multiple bonds exactly for all systems examined so far. Thestrength of OS-CCVB+i3 is highlighted in realistic systems including the[CaMn$_3$O$_4$] cubane subunit of the oxygen-evolving complex and a molecularmagnet with the [Cr$_9$] core unit as well as model systems such as N$_3$,V$_3$O$_3$, and P$_5$. We show that OS-CCVB+i3 is only slightly dependent onthe underlying perfect-pairing reference while OS-CCVB shows a strongerdependence. We also emphasize the compactness of the OS-CCVB+i3 wavefunctioncompared to the heat-bath configuration interaction wavefunction, a recentlyintroduced soft exponential-scaling approach.

journal of chemical physics online/the journal of chemical physics/journal of chemical physics

Open-Shell Coupled-Cluster Valence-Bond Theory Augmented with an  Independent Amplitude Approximation for Three-Pair Correlations: Application  to a Model Oxygen-Evolving Complex and Single Molecular Magnet