Electronic States and Potential Energy Surfaces of NbC2

Abstract

Potential energy surfaces for the low-lying electronic states of NbC2 have been computed using the complete active space multiconfiguration self-consistent field (CASMCSCF) followed by the multireference singles + doubles configuration interaction (MRSDCI) calculations that included up to 2.1 million configurations. The density function theory (DFT) was also employed to study several electronic states of NbC2 near their minima. The DFT results are found to be in good agreement with the CASSCF/MRSDCI results not only for the ground state but also for several excited states, especially with regard to the equilibrium geometries. The dipole moments, vibrational frequencies, and thermodynamic properties are reported. We find a 4B1 state as the ground state of NbC2 with an isosceles triangular equilibrium geometry and dissociation energy of 5.58 eV. The nature of bonding is discussed using the wave function composition and the Mulliken population analysis. The spin−orbit effects were estimated for the ground state.