Excited states of Nb3N2 and Nb3C2: Density functional theory, CASSCF, and MRCI studies

Abstract

Complete active space self-consistent field ͑CASSCF͒ and multireference configuration interaction ͑MRCI͒ methods are used to investigate the Nb 3 N 2 and Nb 3 C 2 clusters in order to determine the agreement between multireference methods, density functional theory ͑DFT͒, and experiment. These two clusters are ideal candidates to study as the known spectroscopy can serve to validate the computational results, yet there is still room for the calculations to inform further spectroscopic experiments. We find that the MRCI leading configuration for each of the ground states is in agreement with that predicted by DFT but only accounts for up to 70% of the total configuration. CASSCF and DFT geometries are also in general agreement. Transition energies between the neutral and cationic manifolds are found to be poorly predicted by MRCI relative to the computationally cheap DFT method. For Nb 3 C 2 we find that a higher energy isomer may have an electronic transition in the spectral vicinity as the lowest energy isomer.

Structural rearrangement in gas phase niobium carbide clusters, Nb C3 and Nb C6

“…Calculations were performed using the M06 method with the Stuttgart/Dresden (SDD) and aug-cc-pVTZ basis sets for niobium and carbon, respectively, to locate a range of geometric isomers for each cluster species at the two lowest spin multiplicities (i.e. singlet & triplet, or doublet & quartet); all other multiplicies were found to be much higher in energy in previous reports [15,16,31]. Geometries for the niobium carbide clusters which contained separated carbon atoms throughout the Nb n cluster motif were taken from previous structures calculated by Dryza et al [15,16].…”

Reactions of Nb2 and Nb3 with CO, D2, N2, and O2: Reconciling experimental kinetics with density functional theory-calculated reaction profiles

“…We have also studied this structure, calculated using the B3LYP density functional, at the complete active space selfconsistent field (CASSCF) and MRCI levels of theory. 41 The reaction path for Nb 2 + N 2 is shown in Figure 6. The singlet (black) and triplet (red) multiplicities are shown.…”