Ab initio ro-vibrational spectroscopy of the group 11 cyanides: CuCN, AgCN, and AuCN

Abstract

Accurate near-equilibrium potential energy and dipole moment functions have been calculated for the linear coinage-metal cyanides CuCN, AgCN, and AuCN using coupled cluster methods and sequences of correlation consistent basis sets. The explicitly correlated CCSD(T)-F12b method is used for the potential energy surfaces (PESs) with inclusion of core correlation, and is combined with contributions from molecular spinorbit coupling, scalar relativity, and effects due to higher order electron correlation. The resulting composite PESs are used in both perturbative and variational calculations of the ro-vibrational spectra. In addition to accurate equilibrium geometries, the ro-vibrational spectra are predicted, which are found to be relatively intense in the 200 -600 cm -1 range due to the bending and metal-carbon stretching modes. The CN stretch near 2165 cm -1 is also predicted to carry enough intensity to allow its observation by experiment. A strong Fermi-resonance is predicted between the first overtone of the bend and the fundamental of the metal-carbon stretch for both CuCN and AgCN. The heats of formation at 0 K are predicted from their calculated atomization energies to be 89.8, 88.6, and 104.5 kcal mol -1 for CuCN, AgCN, and AuCN, respectively. † email addresses: grant. hill@glasgow.ac.uk, Alexander.Mitrushchenkov@univ-mlv.fr, kipeters@wsu.edu 2

Gas Phase Silver Thermochemistry from First Principles

“… a PBE0/aug-cc-pVTZ; see section for details. b Semiexperimental value obtained by combing the ab initio vibration–rotation interaction constants from the composite PESs with the experimental ground state rotational constants; see ref . …”

Ab initio ro-vibronic spectroscopy of SiCCl ($\tilde{X}^2\Pi$X̃2Π)

“…10,11,33,[35][36][37] The spin-orbit and dipole moment surfaces have also been computed ab initio such that the ro-vibronic energy levels and absorption spectrum have been determined from variational calculations. The quality of the PESs and of the spin-orbit surface has lead to a good agreement between the observed LIF values and the present ro-vibronic frequencies.…”

“…Given the success of the current composite approach for ab initio spectroscopy in general, 10,11,33 as well as in the present example, it should be considered the reference for the determination of potential energy surfaces of such Renner-Teller triatomic systems. The resulting PESs must then be treated by variational nuclear motion calculations including the coupling between the molecular angular momenta.…”

“…In the framework of the Born-Oppenheimer approximation, the 2 A and 2 A potential energy surfaces (PESs) associated with theX 2 electronic ground state of SiCCl have been calculated using the MOLPRO package 12 and a composite approach similar to that of Hill et al 10,11 Each energy point was calculated as…”

“…The recent development of explicitly correlated methods coupled with a composite approach allows the determination of highly accurate potential energy surfaces, which, combined with variational nuclear motion calculations, lead to high quality predictive ro-vibronic level energies for such systems. 10,11 Such methodology has been chosen here to study the rovibrational spectroscopy of theX 2 electronic ground state of SiCCl to determine accurate ro-vibronic energy levels in a) Author to whom correspondence should be addressed. Electronic mail:…”