Relativistic effects atomic-number dependence

Theoretical studies on the atomic number dependence of the relative effects on chemical bonding, including polonium, have been carried out, " for example PoFg was investigated. An analysis of bond overlap population using both nonrelativistic and relativistic DV-Xa molecular orbital calculations was... 

Atomic-number dependence of relativistic effects on chemical bonding... 

The Atomic-number dependence of the relativistic effects on chemical bonding has been studied using the difference (APb) in the bond overlap populations between the relativistic and nonrelativistic DV-Xa calculations for various XH diatomic hydrides (X=Cu, Ag, and Au) and XFe hexafluorides (X=S, Se, Mo, Ru, Rh, Te, W, Re, Os, Ir, Pt, U, Np, and Pu). The atomic-number dependence of APb suggests that the absolute values of APb roughly increase with order (aZ)2 for Z up to about 80, and the higher order term (aZ) should be... 

KEYWORDS Relativistic effects bond overlap population atomic-number dependence chemical bonding DV-Xa... 

DV-Xa methods. It was found that relativistic effects become significant in chemical bonding of molecules containing heavy elements with Z larger than 50 and APb of the XFg (X=S to W) shows a Z -dependence similar to that of ARg for the hydrides [1]. On the other hand, the atomic-number dependence of APb for actinide compounds such as UFg was not well explained using the Z -dependence. However, the number of examples examined in the previous work are not satisfactory for discussing the reason for the dependence of APb-... 

The aim of the present work is to obtain the general trend of the atomic-number dependence of the relativistic effects on chemical bonding by examining... 

Atomic-Number Dependence of Relativistic Effects on Chemical Bonding... 

In order to explain the atomic-number dependence of the relativistic effects on chemical bonding, the absolute value of APb, IAPbI, was introduced. Figure 2 shows the plot of IAPbI as a function of Z , along with the results of the six times value of IAPbI for CuH, AgH, and AuH diatomic hydrides. The reason for the... 

Onoe, J. Atomic-number dependence of relativistic effects on chemical bonding. Adv. Quant. Chem. 37, 311-323 (2000)... 

There is still discussion, in particular, in experimentally oriented papers, about whether relativistic effects really exist and are measurable, or if they are an artefact of a wrong theory , namely, the nonrelativistic one, and cannot be measured because in reality there are no nonrelativistic atoms. However, since the notion of relativistic effects is well defined, I claim that they can even be measured in favourable cases directly from the behaviour of a simple function of the atomic number Z. Consider the binding energies of the Is election of hydrogen-like atoms, which are well accessible to measurement. Obviously, this quantity depends on Z, and we attribute the dependence on Z beyond second order to relativity, since nonrelativistic theory predicts that there are no nonvanishing Taylor coefficients beyond second order. The relativistic effect therefore can in this particular case be measured as the deviation of E as a function of Z from parabolic behaviour, a very simple prescription indeed. 

As shown by Fig. 2.9, with the inclusion of the spin-orbit interaction, the observed magic numbers were properly reproduced. The spin-orbit interaction for atomic electrons is a small quantum-relativistic effect. The nuclear spin-orbit coupling is much stronger and results, in addition to relativistic effects, from the spin dependence of the nucleon-nucleon potential. 

The ionization potential of an element is one of its fundamental properties. It is known that the first ionization potential of heavy elements depends on relativistic effects. The Mainz group, in Germany, systematically determined the first ionization potential of the actinide elements from Ac through Es using laser spectroscopy as shown in Table 18.12 (Becke et al. 2002). O Figure 18.24 shows the comparison of ionization potentials between lanthanide and actinide atoms (Moore 1971 Becke et al. 2002). The atomic level structure of Fm (2.7 x 10 ° atoms) with a half-life of 20.1 h was studied for the first time by the method of resonance ionization spectroscopy. Two atomic levels were identified at wave numbers (25,099.8 0.2) cm and (25,111.8 0.2) cm (Sewtz et al. 2003). 

A Relativistic effects are dependent upon atomic number, and become noticeable in the lanthanide series and the elements beyond that series. They affect the enthalpies of atomization of the p-block elements of the 6th period. 

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