Specific features of the electronic structure of super-heavy elements of the 8th period
I. I. Tupitsyn, M. Y. Kaygorodov, D. P. Usov, I.M. Savelyev and V. M. Shabaev
In this work, the results of the electronic-structure calculations for a number of super-heavy elements (SHE) of the 8th period with atomic numbers Z =119-170 are presented [1,2]. Various chemical properties of these elements such as ionization potentials, electron affinities, root mean square radii and widths of the electron-density distribution, electron localization functions (RELF) and Shennon entropy of valence shells are calculated. Based on the obtained results, the role of the relativistic and QED effects on the electronic structures of SHEs was analyzed, and conclusions about the extension of the Mendeleevís periodic law to the region of SHEs were drawn. However, the electronic structure of SHEs is unique in several aspects:
(i) Spin-orbital splitting of valence p-shells reaches up about 10 eV in Og (Z=118) and about 400 eV in element with atomic number Z=165. As a result, due to the strong relativistic contraction, the radial distribution of the electron density of the valence p1/2-shell starts to overlap with the outer core shells and RELF is close to 0.5 in the valence region. In Ref. , this effect in Og was interpreted as smearing out the valence electron density distribution and its approaching to the case of the homogeneous electron gas. A similar effect is observed for the strongly-bound core shells in element with Z = 165. In this case, the electron densities of the 1s- and 2p1/2- shells begin to overlap and the RELF value becomes close to 0.5. However, this behavior of the electron density in the core region cannot indicate that it is close to a homogeneous electron gas.
(ii) Starting from the Z = 125 element, the 5g-shell with the large angular momentum (l = 4) is occupied with electrons. The effective radial potential for the 5g-electron, which includes a large centrifugal repulsive term, has two potential wells which lead to the so-called orbital collapse. In this case, the problem of understanding the meaning of the numerical solutions, and the physical origin of the transition between these two wells arises. The orbital collapse is also observed for the f-electrons in rare-earth elements .
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