Anton, J.

Borschevsky, A.

Pershina, V.

GSI Repository

GSITemplate2007 Theoretical Predictions of Properties of Element 120 and its Adsorption  on Noble Metal Surfaces  V. Pershina1, A. Borschevsky2 and J. Anton3   1GSI, Darmstadt, Germany; 2HIM, Mainz, Germany; 3Institut für Elektrochemie, Universität Ulm, Germany.      In the present work, we predict chemical properties and adsorption behaviour of element 120 whose produc-tion was attempted recently at the GSI, Darmstadt [1]. The most promising nuclear reaction appears to be 50Ti + 249Cf giving the 295120 and 296120 isotopes in the 4n and 3n evaporation channel, respectively [2]. Expected life-time, of the order of µs, is too short for study of chemical properties of this element using current gas-phase chro-matography techniques. However, development of vac-uum chromatography could open new prospects in this field. An analysis of atomic properties, calculated within the Dirac-Coulomb-Breit approach [3], shows that the relativ-istic stabilization and contraction of the valence ns AO in group 2 results in the inversion of trends beyond Ba, so that element 120 will be more electronegative than Ca. In this work, chemical reactivity of element 120 in compari-son with its lighter homologs Ca through Ra was studied on the example of the M2 and MAu dimers. Knowledge of properties of these compounds is indispensable for esti-mating quantities measured in the chromatography stud-ies, i.e., sublimation, ∆Hsub, and adsorption enthalpies, ∆Hads, on gold.  Molecular calculations were performed with the use of our fully relativistic, 4-component, Density Functional Theory method in the non-collinear spin-polarized ap-proximation [4]. Results for M2 and MAu are given in Tables 1 and 2, respectively.  Table 1. Spectroscopic properties of M2 (M = K through element 120): bond lengths, Re (in Å), dissociation ener-gies, De (in eV) and vibrational frequencies, ωe (in cm-1)a Mol. Re De ωe Ca2 4.236 4.277 0.141 0.137 66 65 Sr2 4.493 4.498 0.133 0.137 44 40 Ba2 4.831 0.226 43 Ra2 5.193 0.106 25 (120)2 5.646 0.018 9 a Values in italics are experimental.   The data of Table 1 show that De(M2) have a reversal of the trend beyond Ba. Thus, (120)2 should be most weakly bound in the row of homologs, due to the 8s(120) AO contraction and van der Waals nature of bonding in M2.      De(MAu) (Table 2) have also a reversal of the trend beyond Ba, so that 120Au should be the most weakly bound in the row of homologs due to the 8s(120) AO sta-bilization. ∆Hsub of the 120 metal and ∆Hads(120) on gold were obtained via a correlation with the binding energies of the corresponding dimes in the group. According to the results, ∆Hsub(120) and -∆Hads(120) on Au (also on Pt and Ag) should be the smallest among the homologs.  Table 2. Properties of MAu (M = Ca through element 120): bond lengths, Re (in Å), dissociation energies, De (in eV) and vibrational frequencies, ωe (in cm-1)a Mol. Re De ωe CaAu 2.627 2.67 2.706 2.545 221 221 SrAu 2.808 2.629 159 BaAu 2.869 3.006 145 RaAu 2.995 2.564 105 120Au 3.050 1.902 97 a Values in italics are experimental.   Predicted trends in the adsorption of group-2 elements on noble metals are shown in Fig 1. The moderate values of ∆Hads(120) are indicative of the feasibility of the chro-matography chemical studies on this element.   0,30,81,31,82,32,83,30 50 100 150ZDe(MAu), -∆Hads(M), eVCaSrBaRa120/ Au/ Pt/ Ag      Fig. 1. Calculated De(MAu) (filled symbols) and -∆Hads(M) (open symbols), where M = Ca through element 120, on Au, Pt and Ag.   References [1]  Ch. E. Düllmann, et al., GSI Annual Report 2011.  [2] V. Zagrebaev and W. Greiner, Phys. Rev. C 78, 034610 (2008). [3] A. Borschevsky, et al. Phys. Rev. A, in print.  [4] J. Anton, et al., Phys. Rev. A 69, 012505 (2004). PHN-ENNA-THEORY-10 GSI SCIENTIFIC REPORT 2012224

Theoretical Predictions of Properties of Element 120 and its Adsorption on Noble Metal Surfaces

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Theoretical Predictions of Properties of Element 120 and its Adsorption on Noble Metal Surfaces

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