2026/05/19 by Gregory H. Jones, Aditya Barman, Margarita Shepelenko +2 · 1 citation
Chemistry · Engineering · Physics and Astronomy · #Advanced Chemical Physics Studies #Chemical Thermodynamics and Molecular Structure #Cluster (spacecraft) #Convergence (economics) #Coupled cluster #Cutoff #Extrapolation #Phase Equilibria and Thermodynamics #Thermochemistry
paper · pdf · open access · doi:10.1016/j.cplett.2026.142951
published in Chemical Physics Letters 897, 142951 (Elsevier BV)
openalex publication_date 2026/07/14 · openalex created_date 2026/07/15 · openalex updated_date 2026/08/05
Contributions from connected quintuple excitations in coupled cluster theory can reach the 0.5 kcal mol − 1 range, important enough to matter in accurate computational thermochemistry, yet the very steep ∝ N 12 CPU time scaling impedes routine evaluation. We show that for the differential contribution of quintuples, convergence of a frozen natural orbital (FNO) expansion with respect to the NO cutoff is rapid enough to make FNO-CCSDTQ(5) Λ with cutoffs of 0.0025 or 0.001 viable alternatives. A naive extrapolation to zero cutoff from 0.005,0.0025 works surprisingly well as a low-cost option. Interestingly, FNO convergence is definitely slower for second-row than for first-row compounds.