On relativistic effects in ground state potential curves of Zn₂, Cd₂, and Hg₂ dimers. A CCSD(T) study

Abstract

The ground state potential curves of the Zn2, Cd2, and Hg2 dimers calculated at different levels of theory are presented and compared with each other as well as with experimental and other theoretical studies. The calculations at the level of Dirac-Coulomb Hamiltonian (DCH), 4-component spin-free Hamiltonian, nonrelativistic Lévy-Leblond Hamiltonian and at the level of simple Coulombic correction to DCH are presented. The potential curves are calculated in an all-electron supermolecular approach including the correction to basis set superposition error (BSSE). Electron correlation is treated at the coupled cluster level including single and double excitations and noniterative triple corrections, CCSD(T). In addition, simulations of the temperature dependence of dynamic viscosities in the low-density limit using the obtained ground state potential curves are presented.

Relativistic Time-Dependent Density Functional Theory and Excited States Calculations for the Zinc Dimer

“…The splitting is very small or negligible clearly seen in Figure 1, where we compare visually the 8 lowest states of PBE functional using SFH and the corresponding 16 lowest excited states using 4-component DCH. We note that the CCSD(T) result of [13] for the ground state (see Table 3) using SFH and 4-components DCH confirms our result.…”

“…We also emphasize its importance for heavier relativistic systems [13], although spin-orbit effect is expected to be larger for Cd 2 , Hg 2 , and Cn 2 . Pyper et al [22] pointed out that the relativistic ground-state potential well depth of Hg 2 is 45% of the NR one and clearly it is stronger for Cn 2 .…”

“…DCH. c2 [13] CCSD(T) with SFH. 220 173 9 28 219 136 12 142 P T 219 172 7 27 219 135 13 135 W91 T 218 177 diss 33 220 129 diss 21 P0 T 215 182 9 11 223 135 116 146 GP0 T 216 181 diss 11 226 106 78 38 CB3L T 220 189 diss diss 232 139 137 150 B3L T 211 167 diss 13 215 126 90 139 BL T 210 157 diss 27 207 122 diss 115 B86 T 222 172 diss 37 222 131 14 29 LDA T 247 189 85 45 247 160 89 aug-cc-pVTZ basis set and demonstrate that SFH describes accurately the main relevant contributions of the relativistic effects.…”

“…The covalent contributions to the ground state bonding in the group 12 dimers have been investigated in [12], it was concluded that the bond is a mixture of 3/4 Van der Waals and 1/4 covalent interactions. Bucinisky et al [13] provides spectroscopic constants using the coupled cluster method (CCSD(T)) and different level of the theory 4-component relativistic Hamiltonian, using Dirac-Coulomb Hamiltonian, relativistic spin-free Hamiltonian and nonrelativistic (NR) Hamiltonian. Furthermore, they investigated the relativistic effects and found to be about 5, 8, 19% of the binding energies for Zn 2 , Cd 2 , and Hg 2 , respectively.…”

“…To my experience, generally around zinc (Z = 30) the relativistic effects started to become important for chemical properties. For Hg 2 , they are large enough (for Cn 2 expected to be very large) to make it necessary to incorporate them into any properties that are sensitive to the potential [13]. This is predominantly due to the contraction of 6s orbital, a wellknown and important relativistic effects in heavy atoms [22][23][24][25].…”