QUESTDB_website/data/publis/10/1021/acs/jctc/0c00227/abstract.html

Aiming at completing the sets of FCI-quality transition energies that we recently developed (<i>J. Chem. Theory Comput.</i><b>2018</b>, <i>14</i>, 4360–4379, <i>ibid.</i><b>2019</b>, <i>15</i>, 1939–1956, and <i>ibid.</i><b>2020</b>, <i>16</i>, 1711–1741), we provide, in the present contribution, ultra-accurate vertical excitation energies for a series of “exotic” closed-shell molecules containing F, Cl, P, and Si atoms and small radicals, such as CON and its variants, that were not considered to date in such investigations. This represents a total of 81 high-quality transitions obtained with a series of diffuse-containing basis sets of various sizes. For the exotic compounds, these transitions are used to perform benchmarks with a vast array of lower level models, i.e., CIS(D), EOM-MP2, (SOS/SCS)-CC2, STEOM-CCSD, CCSD, CCSDR(3), CCSDT-3, (SOS-)ADC(2), and ADC(3). Additional comparisons are made with literature data. For the open-shell compounds, we  compared the performance of both the unrestricted and the restricted open-shell CCSD and CC3 formalisms.