Electronic Structure of Scandium and Titanium Carbide Cations, ScC⁺and TiC⁺. Ground and Low-Lying States

Abstract

The monopositive scandium and titanium carbides, ScC + and TiC + , have been studied by multireference methods coupled with quantitative basis sets. We have constructed potential energy curves for the ground and twelve low-lying excited states for both species, focusing on dissociation energies and bonding mechanisms. We have found that the ground states of ScC + and TiC + are of 3 Π and 2 Σ + symmetries, with binding energies (D 0 ) of 68.8 (71.5) and 85.2 (86.7) kcal/mol at the MRCI (MRCI+Davidson correction) level of theory. These values are compared favorably with the corresponding experimental findings, D 0 (ScC + ) ) 77.0 ( 1.4 and D 0 (TiC + ) ) 93.4 ( 5.5 kcal/mol.

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

“…The binding mode consists of 2p and 1/2 bonds and is identical to the one found in the ground X 2 AE þ state of TiC þ [9][10]. The 'extra' electron is placed in an orbital of d symmetry, just observing the chemical bond and defining the spatial symmetry.…”

“…with the 1986 limited MRCI/DZ value of 31.5 kcal mol À1 ) [12]. As our experience with ScC þ , TiC þ , and VC þ indicates [9,10] this value should fall short to an experimental value by about 2-3 kcal mol À1 due to the basis set incompleteness. The final D 0 ( 4 AE À ) value would then equal to about 56 kcal mol À1 , still lower from the experiment by maybe about 10 kcal mol À1 .…”

“…,Cu, the only experimental information available are the dissociation energies of the (unknown symmetry) ground states of ScC þ [4], TiC þ [4], VC þ [5], CrC þ [6], FeC þ [7], and CoC þ [7,8]. Theoretically, and with the help of highly correlated multireference calculations, the symmetries of the ground states of MC þ (M¼Sc, Ti, V, Cr, Fe) have been established [9][10][11] and several low-lying states have been studied for the ScC þ , TiC þ , and FeC þ moieties [10,11]. Older theoretical work by Harrison [12] was focused on the 4 AE À and 4 Å states of CrC þ employing multireference configuration interaction methods coupled with double zeta þ P quality basis sets.…”

“…To obtain reliable spectroscopic parameters, as well as to interpret the bonding nature in their low-lying states, we have performed complete active space selfconsistent field þ singles þ doubles configuration interaction (CASSCF þ 1 þ 2 ¼ MRCI) calculations on the VC þ and CrC þ molecular cations; the present study can be viewed as a continuation of our work on ScC þ , TiC þ [10] and FeC þ [11].…”

A theoretical investigation on the clusters by density functional theory methods

“…In addition, Wang et al [10] have found the first and only spectroscopic and electronic information on TiC x À (x = 2-5) provided by photoelectron spectra. The monopositive titanium carbides, TiC + , have also been studied by multireference methods coupled with quantitative basis sets [11].…”