The low-lying singlet electronic excited states of ZrO2: A symmetry adapted cluster-configuration interaction (SAC-CI) study

The ground electronic state [X(1)A(1)(S-0)] and nine low-lying singlet excited states [2(1)A(1)(S-2), 1(1)A(2)(S-3), 2(1)A(2)(S-6), 1(1)B(1)(S-4), 2(1)B(1)(S-7), 3(1)B(1)(S-11), 1(1)B(2)(S-1), 2(1)B(2)(S-5), and 3(1)B(2)(S-8) states] of ZrO2 were studied using SAC-CI theory. The geometries of the nine electronic excited states were optimized at the SAC-CI/def2-SVP, SAC-CI/def2-SVPD, and SAC-CI/LANL2TZ(f) levels. The vertical excitation energies and adiabatic excitation energies of the selected electronic excited states were calculated by single-point calculations at the SAC-Cl/def2-TZVPPD and SAC-Cl/LANL2TZ(f) levels. Stable C-2v structures for the 1(1)B(2), 2(1)B(2), 3(1)B(2), and 1(1)A(2) states and stable C-s structures for the 1(1)B(1)(A ''), 3(1)B(1)(A ''), and 2(1)A(1)(A') states were determined. For comparison, the unrestricted density functional theory (UBPW91) was also applied to study the X(1)A(1), 1(1)A(2), 1(1)B(1), and 1(1)B(2) states. (C) 2015 Elsevier B.V. All rights reserved.