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 have performed a FCI-quality benchmark calculation for thetetramethyleneethane molecule in cc-pVTZ basis set employing a subset ofCASPT2(6,6) natural orbitals for the FCIQMC calculation. The results are in anexcellent agreement with the previous large scale diffusion Monte Carlocalculations by Pozun et al. and available experimental results. Ourcomputations verified that there is a maximum on PES of the ground singletstate ($^1\text{A}$) $45^{\circ}$ torsional angle and the correspondingvertical singlet-triplet energy gap is $0.01$ eV. We have employed thisbenchmark for assessment of the accuracy of MkCCSDT and DMRG-tailored CCSD(TCCSD) methods. MR MkCCSDT with CAS(2,2) model space, though giving goodvalues for the singlet-triplet energy gap, is not able to properly describe theshape of the multireference singlet PES. Similarly, DMRG(24,25) is not able tocorrectly capture the shape of the singlet surface, due to the missing dynamiccorrelation. On the other hand, the DMRG-tailored CCSD method describes theshape of the ground singlet state with an excellent accuracy, but for thecorrect ordering requires computation of the zero-spin-projection component ofthe triplet state ($^3\text{B}_1$).

Full configuration interaction quantum Monte Carlo benchmark and multireference coupled cluster studies of tetramethyleneethane diradical