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1. Transition Moments for STEOM-CCSD with Core Triples

   https://doi.org/10.1021/acs.jctc.3c00415  

   Simons, Megan; Matthews, Devin A. (August 2023, Journal of Chemical Theory and Computation)
2. Substituted hydrocarbon: a CCSD(T) and local vibrational mode investigation

   https://doi.org/10.1080/00268976.2021.1970844  

   Delgado, Alexis Antoinette; Sethio, Daniel; Matthews, Devin; Oliveira, Vytor; Kraka, Elfi (November 2021, Molecular Physics)
3. Improving MP2 bandgaps with low-scaling approximations to EOM-CCSD

   https://doi.org/10.1063/5.0061242  

   Lange, Malte F.; Berkelbach, Timothy C. (August 2021, The Journal of Chemical Physics)

   null (Ed.)
4. Performance of periodic EOM-CCSD for bandgaps of inorganic semiconductors and insulators

   https://doi.org/10.1063/5.0187856  

   Vo, Ethan A; Wang, Xiao; Berkelbach, Timothy C (January 2024, The Journal of Chemical Physics)

   We calculate bandgaps of 12 inorganic semiconductors and insulators composed of atoms from the first three rows of the Periodic Table using periodic equation-of-motion coupled-cluster theory with single and double excitations (EOM-CCSD). Our calculations are performed with atom-centered triple-zeta basis sets and up to 64 k-points in the Brillouin zone. We analyze the convergence behavior with respect to the number of orbitals and number of k-points sampled using composite corrections and extrapolations to produce our final values. When accounting for electron–phonon corrections to experimental bandgaps, we find that EOM-CCSD has a mean signed error of −0.12 eV and a mean absolute error of 0.42 eV; the largest outliers are C (error of −0.93 eV), BP (−1.00 eV), and LiH (+0.78 eV). Surprisingly, we find that the more affordable partitioned EOM-MP2 theory performs as well as EOM-CCSD. 

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5. Prospects for rank-reduced CCSD(T) in the context of high-accuracy thermochemistry

   https://doi.org/10.1063/5.0230899  

   Zhao, Tingting; Thorpe, James H; Matthews, Devin A (October 2024, The Journal of Chemical Physics)

   Obtaining sub-chemical accuracy (1 kJ mol−1) for reaction energies of medium-sized gas-phase molecules is a longstanding challenge in the field of thermochemical modeling. The perturbative triples correction to coupled-cluster single double triple [CCSD(T)] constitutes an important component of all high-accuracy composite model chemistries that obtain this accuracy but can be a roadblock in the calculation of medium to large systems due to its O(N7) scaling, particularly in HEAT-like model chemistries that eschew separation of core and valence correlation. This study extends the work of Lesiuk [J. Chem. Phys. 156, 064103 (2022)] with new approximate methods and assesses the accuracy of five different approximations of (T) in the context of a subset of molecules selected from the W4-17 dataset. It is demonstrated that all of these approximate methods can achieve sub-0.1 kJ mol−1 accuracy with respect to canonical, density-fitted (T) contributions with a modest number of projectors. The approximation labeled Z̃T appears to offer the best trade-off between cost and accuracy and shows significant promise in an order-of-magnitude reduction in the computational cost of the CCSD(T) component of high-accuracy model chemistries. 

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