Heavy elements, chemical properties predicted

Extensive DFT and PP calculations have permitted the establishment of important trends in chemical bonding, stabilities of oxidation states, crystal-field and SO effects, complexing ability and other properties of the heaviest elements, as well as the role and magnitude of relativistic effects. It was shown that relativistic effects play a dominant role in the electronic structures of the elements of the 7 row and heavier, so that relativistic calculations in the region of the heaviest elements are indispensable. Straight-forward extrapolations of properties from lighter congeners may result in erroneous predictions. The molecular DFT calculations in combination with some physico-chemical models were successful in the application to systems and processes studied experimentally such as adsorption and extraction. For theoretical studies of adsorption processes on the quantum-mechanical level, embedded cluster calculations are under way. RECP were mostly applied to open-shell compounds at the end of the 6d series and the 7p series. Very accurate fully relativistic DFB ab initio methods were used for calculations of the electronic structures of model systems to study relativistic and correlation effects. These methods still need further development, as well as powerful supercomputers to be applied to heavy element systems in a routine manner. Presently, the RECP and DFT methods and their combination are the best way to study the theoretical chemistry of the heaviest elements. 

The predictions of the chemical properties of the superheavy elements discussed in Section IV make it possible to design experiments for their chemical identification should they be produced by heavy-ion bombardement. A few simple preliminary experiments have been performed, utilizing the tandem cyclotron combination at Dubna and the SuperHILAC at Berkeley. 

A basic, old idea of Chemistry is that only a few electrons of an atom or a molecule are directly relevant to its chemical properties. Another basic, newer idea of the Chemistry of heavy elements is that relativity is necessary for its understanding. While the first is a very powerful simplifying idea, the second one increases the complexity of prediction and analysis in Chemistry. The ability of Effective Core Potentials (ECPs) to be, at the same time, the computational realisation of the first idea, and a means to implement very good simplifications of the most rigorous equations of relativistic Quantum Chemistry, lead them to be as popular as they are nowadays. A deep insight into this is offered to the reader in the previous volume of this collection [1]. 

There have been a number of recent predictions of chemical properties of the heavy actinide and transactinide elements based on both atomic calculations and extrapolations of the periodic table, e.g. ground-state electronic configurations, electron binding energies, oxidation states, etc. Thus, we are presently in the exciting position of testing the predictions of the periodic system and the underlying quantum-mechanical calculations on which it is based. 

After the discovery of plutoninm and before elements 95 and 96 were discovered, their existence and properties were predicted. Additionally, chemical and physical properties were predicted to be homologous (similar) to europium (gjEu) and gadolinium ( Gd), located in the rare-earth lanthanide series just above americium (gjAm) and curium ((,jCm) on the periodic table. Once discovered, it was determined that curium is a silvery-white, heavy metal that is chemically more reactive than americium with properties similar to uranium and plutonium. Its melting point is 1,345°C, its boihng point is 1,300°C, and its density is 13.51g/cm. ... 

The chemical composition of carbon blacks (see Section 4.2), as determined by common elemental analysis methods, is of little significance for predicting their properties. Special characteristic properties are, therefore, determined for the characterization and quality control of carbon blacks. Traces of heavy metals are determined spectroscopically in the ash. Copper and manganese ions, etc., are of special interest to the rubber industry because of their interference with the aging process of rubber goods. 

The models and material property data for predicting fission gas release from heavy metal contamination and failed particles are described in Refs. 2 and 3. These models give the release-rate-to-birthrate ratio (R/B) from contamination and failed particles as a function of chemical element, isotope half-life, temperature, and burnup. In addition, the effect of fuel... 

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