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

Novel implementations based on dense tensor storage are presented for thesinglet-reference perfect quadruples (PQ) [Parkhill, Lawler, and Head-Gordon,J. Chem. Phys. 130, 084101 (2009)] and perfect hextuples (PH) [Parkhill andHead-Gordon, J. Chem. Phys. 133, 024103 (2010)] models. The methods areobtained as block decompositions of conventional coupled-cluster theory thatare exact for four electrons in four orbitals (PQ) and six electrons in sixorbitals (PH), but that can also be applied to much larger systems. PQ and PHhave storage requirements that scale as the square, and as the cube of thenumber of active electrons, respectively, and exhibit quartic scaling of thecomputational effort for large systems. Applications of the new implementationsare presented for full-valence calculations on linear polyenes (C n H n+2 ),which highlight the excellent computational scaling of the presentimplementations that can routinely handle active spaces of hundreds ofelectrons. The accuracy of the models is studied in the {\pi} space of thepolyenes, in hydrogen chains (H 50 ), and in the {\pi} space of polyacenemolecules. In all cases, the results compare favorably to density matrixrenormalization group values. With the novel implementation of PQ, activespaces of 140 electrons in 140 orbitals can be solved in a matter of minutes ona single core workstation, and the relatively low polynomial scaling means thatvery large systems are also accessible using parallel computing.

Cost-effective description of strong correlation: efficient implementations of the perfect quadruples and perfect hextuples models