Molecular structure and spectra of titanium and vanadium trifluorides: Complete basis set CCSD(T) study

Abstract

Quantum chemical study on TiF₃ and VF₃ molecules was carried out using the CCSD(T) coupled cluster method using the triple-, quadruple-, and quintuple-zeta basis set and an extrapolation to the complete basis set limit. The methods of multireference configuration interaction MRCISD+Q and perturbation theory MCQDPT2 were used also. The symmetry of the ground electronic state was determined: ² A′₁ and ³ E″ in TiF₃ and VF₃, respectively. The adiabatic excitation energies were evaluated: AEE(TiF₃, $\tilde A^2 E'' \leftarrow \tilde X^2 A'_1$) = 5000 cm⁻¹, AEE(VF₃, $\tilde A^3 A'_2 \leftarrow \tilde X^3 E''$) = 1000 cm⁻¹. The Jahn-Teller effect in $\tilde A^2 E''$ state of TiF₃ and $\tilde X^3 E''$ state of VF₃ was investigated. The computed Jahn-Teller stabilization energy D _3h → C _2v amounts to 555 and 292 cm⁻¹, respectively. The spin-orbit coupling effect on the VF₃ molecular structure and spectrum of electronic states is shown to be quite significant. The calculated vibrational frequencies of TiF₃ are in excellent agreement with IR spectroscopy data. The atomization enthalpies were evaluated: Δ_at H ^pO₂₉₈ = 430 kcal/mol (TiF₃), 393 kcal/mol (VF₃).