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: Δat H 298 pO = 430 kcal/mol (TiF3), 393 kcal/mol (VF3).