Superheavy elements electronic structure

Thus it is obvious that the first step toward predicting chemical and physical properties is to predict the electronic structure of the superheavy elements. An excellent review article on this subject will be published by J. B. Mann [35) in the near future. 

Table 11 illustrates the known closed proton and neutron shells and the predicted closed nuclear shells (shown in parentheses) that might be important in stabilizing the superheavy elements. Included by way of analogy are the long-known closed electron shells observed in the buildup of the electronic structure of atoms. These correspond to the noble gases, and the extra stability of these closed shells is reflected in the relatively small chemical reactivity of these elements. The predicted (in parentheses) closed electronic structures occur at Z = 118 and Z = 168. 

Except for few properties, like volatility or complex formation, many others cannot be directly measured for the heaviest element compormds. They can only be evaluated. For example, the chemical composition of superheavy element compounds is not known and can only be assumed on the basis of analogy in the experimental behaviour with that of the lighter congeners in chemical groups. Ionisation potentials (IP), electron affinities (EA), dissociation energies or geometrical structures can not presently be measured at all, and can only be determined via quantum-chemical calculations. Thus, in the area of the heaviest elements theory starts to become extremely important and is often the only source of useful chemical information. 

Due to the very strong relativistic effects, the chemistry of those superheavy elements will be very different to anything known before. Without relativistic effects, it would also be different to that of their lighter homologs due to very large shell structure effects [26]. It will be a challenge for theoreticians to acciuately predict electronic states of those superheavy elements. 

T. Saue, L. Visscher. Four-component electronic structure methods for molecules. In S. Wilson, U. Kaldor, Ed., Theoretical Chemistry and Physics of Heavy and Superheavy Elements, p. 211-267, Dordrecht, 2003. Kluwer. 

Experimentally, an inertness/reactivity of Cn was supposed to be investigated by studying its volatility with respect to that of Hg and Rn as adsorption on a gold surface (gold plated detectors) of the chromatography column used in gas-phase chromatography experiments [201-203] ( Gas-Phase Chemistry of Superheavy Elements ). The questions to the modern electronic structure theory, therefore, were Is Cn metallic in the solid state, or is it more like a solid noble gas What is its Af/sut How volatile and reactive towards gold is the Cn atom in comparison with Hg and Rn ... 

Pershina, V. The Chemistry of the superheavy elements and relativistic effects. In Schwerdtfeger, P. (ed.) Relativistic Electronic Structure Theory, Part II, pp. 1-80. Elsevier, Amsterdam (2002)... 

Hermann, A., Fuithmuller, J., Gaggeler, H.W., Schwerdtfeger, P. Spin-oibit effects in structural and electronic jnoperties for the solid state of the group-14 elements from carbon to superheavy element 114. Phys. Rev. B 82, 155116(8) (2010)... 

Nash, C.S., Bursten, B.E. Spin-orbit, VSEPR theory, and the electronic structure of heavy and superheavy group IVA hydrides and group VIIIA tetrafluorides. A partial role reversal for elements 114 and 118. J. Phys. Chem. A 103, 402-410 (1999)... 

Elements near present upper boundary 1629 Electronic structure of superheavy elements 1633 Predictions of chemical properties of superheavy elements 1635... 

Guided by a judicious combination of consideration of the calculated electronic structures, the periodic table (as shown in Figs 24.1 and 24.2X and various well-established qualitative chemical theories, scientists have been able to make some detailed predictions of the chemical properties of the superheavy elements. Of course, at first these elements will at best be produced one atom at a time , and they offer scant hope for ultimate production in the macroscopic quantities that would be required to verify some of these predictions. However, many of the predicted specific macroscopic properties, as well as the more general properties predicted for the other elements, will be useful in designing tracer experiments for the chemical identification of any of these elements that might be synthesized. 

Although all of the superheavy elements will show relativistic effects in their chemistry, the clearest case may be element 115 (eka-bismuth), which we have used for illustration above. Keller, Nestor, and Fricke [25] have made some detailed predictions of the chemical properties of element 115 based on extrapolations of the properties of elements of group V and relativistic calculations of electronic structure. Their results indicate that the chemical... 

The early density functional work has been reviewed before. More recently, Kaldor s group investigated the electronic structures of the superheavy elements 115 and 117 to 122. ... 

A. V. Titov, N. S. Mosyagin, T. A. Isaev, and A. N. Petrov, Accuracy and efficiency of modem methods for electronic structure calculation on heavy- and superheavy-element compounds, Phys. At. NucL, 66, 1152-1162 (2003). 

Energy levels of heavy and super-heavy (Z>100) elements are calculated by the relativistic coupled cluster method. The method starts from the four-component solutions of the Dirac-Fock or Dirac-Fock-Breit equations, and correlates them by the coupled-cluster approach. Simultaneous inclusion of relativistic terms in the Hamiltonian (to order o , where a is the fine-structure constant) and correlation effects (all products smd powers of single and double virtual excitations) is achieved. The Fock-space coupled-cluster method yields directly transition energies (ionization potentials, excitation energies, electron affinities). Results are in good agreement (usually better than 0.1 eV) with known experimental values. Properties of superheavy atoms which are not known experimentally can be predicted. Examples include the nature of the ground states of elements 104 md 111. Molecular applications are also presented. 

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