Properties of NoO\nand YbO

Bond dissociation energies (BDEs) and spectroscopic parameters\nfor the ground states of YbO and NoO were calculated at the Brueckner\ndoubles (BD(T)) level and for NoO at the coupled cluster CCSD(T) level\nbased on the closed-shell configurations Yb<sup>2+</sup>(4f<sup>14</sup>)O<sup>2–</sup>(2p<sup>6</sup>) and No<sup>2+</sup>(5f<sup>14</sup>)O<sup>2–</sup>(2p<sup>6</sup>). For YbO, the BD(T)\nBDE (3.93 eV) and vibrational frequency (686.3 cm<sup>–1</sup>) are consistent with the experiment; the BD(T) bond distance was\n1.8492 Å, about 0.04 Å longer than the experiment. For NoO,\nthe calculated BDEs are 3.07 eV (BD(T)) and 3.08 eV (CCSD(T)) and\nare expected to be good to ±3 kcal/mol (±0.13 eV). Potential\nenergy curves (PECs) for the spin–orbit (Ω) states associated\nwith the f<sup>13</sup>s<sup>1</sup> configurations of YbO and NoO\nwere calculated at the SA-CASSCF/SO-CASPT2/aQ-DK level. PECs considering\nboth the f<sup>13</sup>s<sup>1</sup> and f<sup>14</sup> configurations\nwere calculated at this level, as the ground states are expected to\ncontain both configurations. Due to a bias in the SA-CASSCF to the\nf<sup>13</sup>s<sup>1</sup> configurations, the f<sup>14</sup> configurations\ncould not be properly described simultaneously with the f<sup>13</sup>s<sup>1</sup> ones. The natural population analysis based on the\nnatural bond orbitals shows that YbO and NoO are quite ionic, with\n5d orbitals being more important in YbO than the 6d orbitals in NoO.