Electronic structure of vanadium and chromium carbide cations, VC⁺and CrC⁺. Ground and low-lying states

Abstract

The ground and low-lying states of the monopositive vanadium and chromium carbides, VC þ and CrC þ have been studied by multireference methods and quantitative basis sets. Potential energy curves for 17 (VC þ ) and 19 (CrC þ ) states have been fully calculated. A variety of binding modes is revealed in the low-lying spectrum of the two molecular cations, often accompanied with an electronic charge transfer from the metal cation towards carbon. Two states compete for the ground state identity in both systems. One state comprises two p and ½ bonds (similarly to ScC þ and TiC þ ), while the other state forms a genuine triple bond. After a rather intricate analysis including core electron effects, scalar relativity and curve shifts, the formal ground states of VC þ and CrC þ are found to be of 3 Á and 2 Á symmetry, with estimated energy differences from the competing 1 AE þ and 4 AE À states of 1-3 and 3-7 kcal/mol, respectively. At the highest level of theory including core/valence correlation and one-electron relativistic effects, the calculated ground-state binding energies are in satisfactory agreement with available experimental values.

Electronic spectroscopy and electronic structure of diatomic CrC

“…22; with respect to the ground state atoms D e 0 ͑D 0 0 ͒ =95͑94͒ − ⌬E MRCI+Q ͑ 5 S ← 7 S͒ =75͑74͒ kcal/ mol. 49. It should be mentioned that the potential energy curve of the X 3 ⌺ − state displayed in Fig.…”

High-Level Ab Initio Predictions for the Ionization Energy, Bond Dissociation Energies, and Heats of Formation of Vanadium Methylidyne Radical and Its Cation (VCH/VCH+)

“…Transition-metal (M)-containing molecules are in the spot light in a myriad of active scientific fields, including catalytic and biological processes, material chemistry, and astrophysics. − However, their recognized importance is at odds with the scarcity of accurate experimental investigations − and accompanying high-level theoretical calculations on their energetic properties. − Even for model diatomic transition-metal oxides, nitrides, carbides, and hydrides (MX, X = O, N, C, and H), reliable computational benchmarking efforts are still far from sufficient. − Expectedly, such a need among triatomic M-containing molecules is likewise pressing. Among organometallic complexes, triatomic M-methylidyne (MCH) is probably the first system being brought to the forefront of high-resolution spectroscopic characterization. − The laser-induced fluorescence spectra of vanadium methylidyne (VCH), a product of the reaction between vanadium and methane was found to be extremely complex despite having the simplest possible structure among M-carbyne species. , The ground state and various excited states have been studied using ab initio multireference configuration interaction (MRCI) methods.…”

Rotationally resolved state-to-state photoionization and the photoelectron study of vanadium monocarbide and its cations (VC/VC+)

“…Three electronic states, 3 D, 1 S + , and 1 D, were shown to be good candidates for the ground electronic state of VC + . 14 Based on density functional (DFT) calculations, Gutsev et al 13 have reported energetic and spectroscopic predictions for the VC + (X) ground state. Their DFT calculations also yielded an IE prediction for VC to be IE(VC) = 7.36 eV.…”

“…This study predicts 3 D to be the ground electronic state with the 1 S + and 1 D states to situate at 0.13 and 0.36 eV, respectively, above its ground state. 14 To date, the only experimental energetic information available for VC + has been its 0 K bond dissociation energy (D 0 ), which was reported 15,16 to be 3.87 AE 0.14 and 3.95 AE 0.04 eV based on two guided ion beam ion-molecule collision studies.…”