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).

Author(s) Lam, C.S.; Lau, K.C.; Ng, C.Y.
Journal J Phys Chem A
Date Published 2019 Aug 15

The ionization energy (IE) of VCH, the 0 K V-CH/VC-H bond dissociation energies (s), and the heats of formation at 0 K (Δ) and 298 K (Δ) for VCH/VCH are predicted by the wave function-based CCSDTQ/CBS approach. This composite-coupled cluster method includes full quadruple excitations in conjunction with the approximation to the complete basis set (CBS) limit. The contributions of zero-point vibrational energy, core-valence (CV) correlation, spin-orbit coupling, and scalar relativistic corrections are taken into account. The present calculations show that adiabatic IE(VCH) = 6.785 eV and demonstrate excellent agreement with an IE value of 6.774 7 ± 0.000 1 eV measured with two-color laser-pulsed field ionization-photoelectron spectroscopy. The CCSDT and MRCI+Q methods which include CV correlations give the best predictions of harmonic frequencies: ω (ω) (bending) = 534 (650) and 564 (641) cm and the V-CH stretching ω (ω) = 835 (827) and 856 (857) cm compared with the experimental values. In this work, we offer a streamlined CCSDTQ/CBS approach which shows an error limit (≤20 meV) matching with previous benchmarking efforts for reliable IE and predictions for VCH/VCH. The CCSDTQ/CBS (V-CH) - (V-CH) = -0.012 eV and (VC-H) - (VC-H) = 0.345 eV are in good accord with the experimentally derived values of -0.028 4 ± 0.000 1 and 0.355 9 ± 0.000 1 eV, respectively. The present study has demonstrated that the CCSDTQ/CBS protocol can be readily extended to investigate triatomic molecules containing 3d-metals.

DOI 10.1021/acs.jpca.9b05493
ISSN 1520-5215
Citation J Phys Chem A. 2019.

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