JAHN-TELLER EFFECT IN $VCl_{4}$
Loading...
Date
1977
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
Ab initio restricted Hartree-Fock calculations have been carried out on the $3e^{1} ^{2}E$ ground state of $VCl_{4}$ using a contracted Gaussian basis set of (14s11p5d/12s9p), [9s7p2d/6s4p]. The effects of the Jahn-Teller active E vibration were studied by computing the energy when opposite bond angles were simultaneously changed by $3^\circ, 6^\circ, -3^\circ, -6^\circ$. The potential energy surface is described by $$W = W(T_{d}) + 1/2 kr^{2} \pm (ar + 1/2 k^{\prime} r^{2} \cos3\varphi)$$ where r, $\varphi$ are the vibrational coordinates in polar form, and k, a, and $k^{\prime}$ are potential constants. The minimum energy occurs with opposite angles opened by $3.1^\circ$, and is 118 $cm^{-1}$ below the tetrahedral energy. Closing these angles by $3.0^\circ$ corresponds to a saddle point on the surface which is 3 $cm^{-1}$ higher in energy. Vibronic energies were calculated using a diabatic, harmonic oscillator expansion. The lowest energy level was found to be 32 $cm^{-1}$ below the tetrahedral energy, and all others to be above the tetrahedral energy. Thus, there is no static distortion, and the dynamic effects agree with those found by electron $diffraction.^{1,2}$ A comparison calculation of the E vibrational frequency in $TiCl_{4}$ gave 128 $cm^{-1}$ vs. the measured 118 $cm^{-1}$.
Description
$^{1}$Y. Morino and H. Uehara, J. Chem. Phys. 45, 4543 (1966). $^{2}$ H. Seip, Tidsskr. Kjemi, Bergv. Mettallurgi 28, 177 (1968), English translation available from R. M. Pitzer.
Author Institution: Department of Chemistry, The Ohio State University
Author Institution: Department of Chemistry, The Ohio State University