Issue 15, 2005

Accurate ab initio determination of spectroscopic and thermochemical properties of mono- and dichlorocarbenes

Abstract

The best technically feasible values for the triplet–singlet energy gap and the enthalpies of formation of the HCCl and CCl2 radicals have been determined through the focal-point approach. The electronic structure computations were based on high-level coupled cluster (CC) methods, up to quadruple excitations (CCSDTQ), and large-size correlation-consistent basis sets, ranging from aug-cc-pVDZ to aug-cc-pV6Z, followed by extrapolation to the complete basis set limit. Small corrections due to core correlation, relativistic effects, diagonal Born–Oppenheimer correction, as well as harmonic and anharmonic zero-point vibrational energy corrections have been taken into account. The final estimates for the triplet–singlet energy gap, T0(ã), are 2170 ± 40 cm−1 for HCCl and 7045 ± 60 cm−1 for CCl2, favoring the singlet states in both cases. Complete quartic force fields in internal coordinates have been computed for both the [X with combining tilde] and ã states of both radicals at the frozen-core CCSD(T)/aug-cc-pVQZ level. Using these force fields vibrational energy levels of {HCCl, DCCl, CCl2} up to {6000, 5000, 7000} cm−1 were calculated both by second-order vibrational perturbation theory (VPT2) and variationally. These results, especially the variational ones, show excellent agreement with the experimentally determined energy levels. The enthalpies of formation of HCCl ([X with combining tilde]1A) and CCl2([X with combining tilde]1A1), at 0 K, are 76.28 ± 0.20 and 54.54 ± 0.20 kcal mol−1, respectively.

Graphical abstract: Accurate ab initio determination of spectroscopic and thermochemical properties of mono- and dichlorocarbenes

Supplementary files

Additions and corrections

Article information

Article type
Paper
Submitted
13 May 2005
Accepted
15 Jun 2005
First published
06 Jul 2005

Phys. Chem. Chem. Phys., 2005,7, 2881-2893

Accurate ab initio determination of spectroscopic and thermochemical properties of mono- and dichlorocarbenes

G. Tarczay, T. A. Miller, G. Czakó and A. G. Császár, Phys. Chem. Chem. Phys., 2005, 7, 2881 DOI: 10.1039/B506790A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements