Borschevsky, A.

Eliav, E.

Kaldor, U.

Pershina, V.

GSI Repository

Relativistic coupled cluster study of the MAu and M2 dimers of Hg, Cn, and FlA. Borschevsky1, V. Pershina2, E. Eliav3, and U. Kaldor31HIM, Mainz, Germany; 2GSI, Darmstadt, Germany; 3Tel Aviv University, Tel Aviv, IsraelThe electronic structure of Cn (Z=112) and Fl (Z=114)experiences strong relativistic effects due to the relativisticstabilization and contraction of their valence orbitals, the7s orbital in case of Cn, and the 7p1/2 orbital in case of Fl.Thus, their molecular and chemical properties are expectedto be determined by relativity.These two elements are the heaviest atoms studied inchemical experiments. Their relative inertness makes themgood candidates for studies of volatility through their ad-sorption on metal surfaces (such as gold) using the gas-phase thermochromatography technique [1, 2]. By per-forming calculations of the binding energy of the MAudimers, the trends in the adsorption enthalpies of the atomson a gold surface, −ΔHAuads(M), can be estimated. Bond-ing of an element in the solid state in the first approxima-tion can be described by the bonding in its M2 dimer. Thus,in order to obtain a theoretical insight into the trends in thebinding of Hg, Cn, and Fl to a gold surface, and their bind-ing in a solid, ab initio study of the molecular properties oftheir MAu and M2 dimers was performed.The calculations were carried out within the infinite-order two-component relativistic Hamiltonian obtained af-ter the Barysz-Sadlej-Snijders (BSS) transformation of theDirac Hamiltonian in a finite basis set [3]. This methodtreats scalar and spin-orbit relativistic effects simultane-ously, and for valence molecular properties achieves sim-ilar accuracy to that of the 4-component Dirac Hamilto-nian, while significantly reducing the computational effort.Electron correlation was treated in the framework of thesingle reference coupled cluster approach with single, dou-ble, and perturbative triple excitations (CCSD(T)). Fae-gri’s dual family basis sets [4] were used; the basis setswere extended to convergence of the calculated molecularproperties. All the calculations were performed using theDIRAC08 computational program package [5].Table I contains the calculated bond lengths,Re, and dis-sociation energies,De, of the MAu and M2 molecules. Hg2is the only system for which experimental parameters areavailable [6]. The excellent agreement of the calculatedbinding energy with the experiment in case of Hg2 lendscredence to our predictions for the rest of the systems.The calculated trend in the bond length of the MAumolecules is Re(FlAu)>Re(CnAu)>Re(HgAu). The in-crease inRe from HgAu to CnAu corresponds to the weak-ening of the bond in CnAu, and the Re of FlAu is largerthan that of CnAu due to the participation of the more dif-fuse 7p1/2 and 7p3/2 orbitals of Fl in the bond [7]. Thepresent calculations predict the HgAu molecule to be themost stable of the three, followed by FlAu, and CnAu asTable 1: Equilibrium bond lengths, Re (in A˚), and dissoci-ation energies,De (in eV ), of the MAu and M2 molecules.The values in parenthesis are experimental for Hg2 [6].HgAu CnAu FlAuRe 2.640 2.720 2.791De 0.563 0.368 0.446Hg2 Cn2 Fl2Re 3.744 (3.69) 3.461 3.547De 0.050 (0.046) 0.084 0.117the least stable. Bonding in CnAu is weaker than in HgAudue to the strong relativistic stabilization of the 7s orbitalin Cn compared to the 6s in Hg. FlAu should be strongerbound than CnAu due to the 7p1/2 orbital in Fl being moreaccessible than the 7s of Cn for the bonding with the 6sorbital of gold [7]. Assuming that the trends in the bind-ing energies of the gold containing diatomic molecules area good indication of the trends in the adsorption enthalpiesof the atoms on a gold surface, according to the current cal-culations Fl should be stronger adsorbed on gold than Cn.Comparing the results for the three M2 dimers, weobserve that Hg2 has the longest and Cn2 the short-est bond. The trend in the dissociation energy is De(Fl2)>De(Cn2)>De(Hg2). Cn2 and Hg2 dimers behave asvan der Waals systems; thus Cn2 has a higher dissociationenergy of the two, due to the strong relativistic contractionof the 7s orbital, which causes a decrease ofRvdW(Cn) anda subsequent increase in the binding energy of the dimer.Group-14 elements, including Fl, behave like chemicallybound systems, whereDe decreases withZ due to the spin-orbit splitting and the relativistic stabilization of the np1/2orbital. Thus, Fl2 is the least bound dimer in group 14[7]; however, due to the different type of interaction, it isstronger bound than both Hg2 and Cn2.References[1] R. Eichler et al., Nature 447, 72 (2007)[2] A. Yakushev et al., Inorg. Chem. 53, 1624 (2014)[3] M. Iliasˇ and T. Saue, J. Chem. Phys. 126, 064102 (2007)[4] K. Faegri, Theor. Chim. Acta 105, 252 (2001)[5] DIRAC08 program package (http://diracprogram.org/)[6] J. Koperski, J.B. Atkinson, and L. Krause, J. Mol.Spectrosc.184, 300 (1997); Can. J. Phys. 72, 1070 (1994)[7] V. Pershina et al., J. Chem. Phys. 131, 084713 (2009)GSI SCIENTIFIC REPORT 2013 NUSTAR-SHE-09doi:10.15120/GR-2014-1-NUSTAR-SHE-09 133 NUSTAR-SHE-09 GSI SCIENTIFIC REPORT 2013134 doi:10.15120/GR-2014-1-NUSTAR-SHE-09

Relativistic coupled cluster study of the MAu and $M_2$ dimers of Hg, Cn, and Fl

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Relativistic coupled cluster study of the MAu and $M_2$ dimers of Hg, Cn, and Fl

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Relativistic coupled cluster study of the MAu and M2M_2M2​ dimers of Hg, Cn, and Fl

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Relativistic coupled cluster study of the MAu and $M_2$ dimers of Hg, Cn, and Fl