Detailed Pair Natural Orbital-Based Coupled Cluster Studies of Spin Crossover Energetics

• DOI: 10.1021/acs.jctc.9b01109
• Publication Date: 2020-03-20T17:58:37Z
• Authors: Benedikt M. Flöser; Yang Guo; Christoph Riplinger; Felix Tuczek; Frank Neese
• Keywords: Coupled cluster; Basis (linear algebra)

In this work, a detailed study of spin-state splittings in three spin crossover model compounds with DLPNO-CCSD(T) is presented. The performance comparison to canonical CCSD(T) assessed detail. It was found that chemical accuracy, compared the results, are achieved when full iterative triples (T1) scheme and TightPNO settings applied relativistic effects taken into account. Having established level accuracy can be reached relative we have undertaken basis set second part study. slow convergence results correlated calculations respect extension particularly acute for reasons discussed detail Article. fact, some studied systems, 5Z sets necessary order come close limit estimated here by extrapolation. Finally, present work available literature. general, acceptable agreement previous found, although notable deviations stemming from differences methodology noted. noted published CASPT2 numbers far away extrapolated numbers. addition, dynamic quantum Monte Carlo differ several tens kcal/mol A DFT produced range popular density functionals shows expected scattering showcases difficulty applying energies.