Results of the DiracSlater discrete variational calculations for the group 4,5, and 6 highest chlorides including elements 104, 105, and 106 have shown that the groups are not identical with respect to trends in the electronic structure and bonding. The charge density distribution data show that notwithstanding the basic increase in covalency within the groups this increase diminishes in going from group 4 to group 6. As a result, E106C16 will be less stable toward thermal decomposition than W C L which is confirmed by an estimated low E 1 0 6 4 1 bond energy. AHform equal to -90.3 f 6 kcal/mol is obtained for ElO6Cl6 in the gas phase, which is indicative of a very low stability of this compound. The stability of the maximum oxidation state is shown to decrease in the direction E104(+4) > E105(+5) > E106(+6).

Element 105 / Hahnium / Transactinide chemistry / Relativistic molecular calculations / Hydrolysis SummaryRelativistic molecular orbital calculations of the electronic structure of hydrated and hydrolyzed complexes have been performed for group 5 elements Nb, Ta, Ha and their pseudohomolog, Pa. On their basis, relative values of the free energy changes and constants of hydrolysis reactions were defined. These results show that hydrolysis decreases in the order Nb > Ta > Ha > Pa, which for Nb, Ta and Pa is in agreement with experiment. A decisive factor in the process turned out to be a predominant electrostatic metal-ligand interaction.

Element 105 / Hahnium / Chemical properties / Group 5 elements / Relativistic molecular orbital calculations AbstractTo study the complex formation of group 5 elements (Nb, Ta, Ha, and pseudoanalog Pa) in aqueous HCl solutions of medium and high concentrations the electronic structures of anionic complexes of these elements [MC1 6 ]~, [MOCLJ", [M(OH) 2 Cl 4 ]~, and [MOCI5] 2 " have been calculated using the relativistic DiracSlater Discrete-Variational Method. The charge density distribution analysis has shown that tantalum occupies a specific position in the group and has the highest tendency to form the pure halide complex, [TaCl 6 ] ~. This fact along with a high covalency of this complex explains its good extractability into aliphatic amines. Niobium has equal trends to form pure halide [NbCl 6 ]~ and oxyhalide [NbOCl 5 ] 2 " species at medium and high acid concentrations. Protactinium has a slight preference for the [PaOCl 5 ] 2-form or for the pure halide complexes with coordination number higher than 6 under these conditions. Element 105 at high HCl concentrations will have a preference to form oxyhalide anionic complex [HaOCl 5 ] 2~ rather than [HaCl 6 ] ". For the same sort of anionic oxychloride complexes an estimate has been done of their partition between the organic and aqueous phases in the extraction by aliphatic amines, which shows the following succession of the partition coefficients: Ρ Nb < Phu < ipa·

Relativistic self-consistent charge Dirac–Slater discrete variational method calculations have been done for the series of molecules MBr5, where M=Nb, Ta, Pa, and element 105, Ha. The electronic structure data show that the trends within the group 5 pentabromides resemble those for the corresponding pentaclorides with the latter being more ionic. Estimation of the volatility of group 5 bromides has been done on the basis of the molecular orbital calculations. According to the results of the theoretical interpretation HaBr5 seems to be more volatile than NbBr5 and TaBr5.

Electronic structures of MOCl3 and MOBr3 molecules, where M=V, Nb, Ta, Pa, and element 105, hahnium, have been calculated using the relativistic Dirac–Slater discrete-variational method. The character of bonding has been analyzed using the Mulliken population analysis of the molecular orbitals. It was shown that hahnium oxytrihalides have similar properties to oxytrihalides of Nb and Ta and that hahnium has the highest tendency to form double bond with oxygen. Some peculiarities in the electronic structure of HaOCl3 and HaOBr3 result from relativistic effects. Volatilities of the oxytrihalides in comparison with the corresponding pentahalides were considered using results of the present calculations. Higher ionic character and lower covalency as well as the presence of dipole moments in MOX3 (X=Cl, Br) molecules compared to analogous MX5 ones are the factors contributing to their lower volatilities.

The interaction of the inert gases Rn and element 118 with various surfaces has been studied on the basis of fully relativistic ab initio Dirac-Coulomb CCSD(T) calculations of atomic properties. The calculated polarizability of element 118, 46.3 a.u., is the largest in group 18, the ionization potential is the lowest at 8.91 eV, and the estimated atomic radius is the largest, 4.55 a.u. These extreme values reflect, in addition to the general trends in the Periodic Table, the relativistic expansion and destabilization of the outer valence 7p(3/2) orbital. Van der Waals coefficients C(3) and adsorption enthalpies DeltaH(ads) of Ne through element 118 on noble metals and inert surfaces, such as quartz, ice, Teflon, and graphite, were calculated in a physisorption model using the atomic properties obtained. The C(3) coefficients were shown to steadily increase in group 18, while the increase in DeltaH(ads) from Ne to Rn does not continue to element 118: The large atomic radius of the latter element is responsible for a decrease in the interaction energy. We therefore predict that experimental distinction between Rn and 118 by adsorption on these types of surfaces will not be feasible. A possible candidate for separating the two elements is charcoal; further study is needed to test this possibility.

A detailed study of the electronic structure and bonding of the pentahalides of group 5 elements V, Nb, Ta, and element 105, hahnium (and Pa) has been carried out using relativistic molecular cluster Dirac–Slater discrete-variational method. A number of calculations have been performed for different geometries and molecular bond distances. The character of the bonding has been analyzed using the Mulliken population analysis of the molecular orbitals. It is shown that hahnium is a typical group 5 element. In a great number of properties it continues trends in the group. Some peculiarities in the electronic structure of HaCl5 result from relativistic effects.

Results of relativistic (Dirac-Slater and Dirac-Fock) and nonrelativistic (Hartree-Fock-Slater) atomic and molecular calculations have been compared for the group 5 elements Nb, Ta, and Ha and their compounds MCl, to elucidate the influence of relativistic effects on their properties especially in going from the 5d element Ta to the 6d element Ha. The analysis of the radial distribution of the valence electrons ofthe metals for electronic configurations obtained as a result of the molecular calculations and their overlap with ligands show opposite trends in behavior for nSI/2' npl/2' and (n-1)d S / 2 orbitals for Ta and Ha in the relativistic and nonrelativistic cases. Relativistic contraction and energetic stabilization of the nSI/2 and npl/2 wave functions and expansion and destabilization of the (n-1)d S / 2 orbitals make hahnium pentahalide more covalent than tantalum pentahalide and increase the bond strength. The nonrelativistic treatment of the wave functions results in an increase in ionicity of the MCI s molecules in going from Nb to Ha making element Ha an analog ofV. Different trends for the relativistic and nonrelativistic cases are also found for ionization potentials, electronic affinities, and energies of charge-transfer transitions as well as the stability of the maximum oxidation state.