Abstract
The potential energy curves and the NMR properties: nuclear spin–spin coupling constants and nuclear shielding constants have been calculated for Zn2, Cd2 and Hg2 dimers using density functional theory. The calculations have been carried out using the relativistic four-component Dirac–Coulomb Hamiltonian, and, in the case of energy curves, also relativistic effective core potentials. In case of NMR parameters, the relativistic effects turned out to be critically important even for the lightest dimer, Zn2. The importance of the spin–orbit coupling depends on the internuclear distance: these effects tend to be significant for short internuclear distances.
Highlights
Mercury has an additional aspect attracting attention of computational chemistry: the nucleus of 199 Hg has a 1/2 spin and relatively high abundance, making 199 Hg NMR a suitable tool for investigation of mercury complexes. We explore both aspects of Zn2, Cd2 and H g2 dimers in this contribution: energetics and nuclear magnetic resonance properties
The present study is carried out using relativistic fourcomponent Dirac–Coulomb Hamiltonian, which allows us to take into account the relativistic effects in the most complete way available for NMR properties. (It should be kept in mind, that this is not a fully relativistic Hamiltonian and that the first-order Breit correction to the missing terms may quite significantly contribute to the calculated NMR properties of mercury [20])
The potential energy curves for dimers under consideration have been computed with the use of coupledcluster method (CCSD and CCSD(T) models), four-component Dirac–Coulomb Hamiltonian [31] and DZP basis set [32,33,34] by means of Dirac [35]
Summary
Closed-shell van der Waals metal dimers are of scientific interest [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17] for their own sake, due to the possibility of laser applications (in analogy with the homo- and heteroatomic noble gas excimers and exciplexes [18]), and as the smallest metal clusters, providing information relevant for the study of condensation processes. Mercury has an additional aspect attracting attention of computational chemistry: the nucleus of 199 Hg has a 1/2 spin and relatively high abundance, making 199 Hg NMR a suitable tool for investigation of mercury complexes. We explore both aspects of Zn2, Cd2 and H g2 dimers in this contribution: energetics and nuclear magnetic resonance properties. We compare the potential energy curves calculated using the four-component Hamiltonian with the results of calculations carried out by means of one-component Hamiltonian with effective core potentials Another methodological issue under consideration is the performance of different exchange correlation density functionals in comparison with the coupled cluster calculations.
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