Reference Vertical Excitation Energies for Transition Metal Compounds

To
enrich and enhance the diversity of the quest database
of highly accurate excitation energies [Véril, M.; et al. Wiley Interdiscip. Rev.: Comput.
Mol. Sci. 2021, 11, e1517], we report vertical transition energies
in transition metal compounds. Eleven diatomic molecules with a singlet
or doublet ground state containing a fourth-row transition metal (CuCl,
CuF, CuH, ScF, ScH, ScO, ScS, TiN, ZnH, ZnO, and ZnS) are considered,
and the corresponding excitation energies are computed using high-level
coupled-cluster (CC) methods, namely, CC3, CCSDT, CC4, and CCSDTQ,
as well as multiconfigurational methods such as CASPT2 and NEVPT2.
In many cases, to provide more comprehensive benchmark data, we also
provide full configuration interaction estimates computed with the
configuration interaction using a perturbative selection made iteratively
(CIPSI) method. Based on these calculations, theoretical best estimates
of the transition energies are established in both the aug-cc-pVDZ
and aug-cc-pVTZ basis sets. This allows us to accurately assess the
performance of the CC and multiconfigurational methods for this specific
set of challenging transitions. Furthermore, comparisons with experimental
data and previous theoretical results are also reported.