Search

Multiconfiguration Dirac-Fock method is employed to calculate the excitation energies, ionization potentials, oscillator strengths, and radii for all neutral and up to four times ionized species of element Uuq, as well as the homolog elements Ge, Sn, and Pb. Using an extrapolative scheme, improved ionization potentials of Uuq were obtained with an uncertainty of less than 2000 cm-1. Two relatively stronger resonance transitions are predicted for the element Uuq. In particular, the strongest line in Uuq, corresponding to the [6d107s27p3/28s1/2]1→[6d107s27p3/22]2 transition at 22 343 cm-1, just lies in the prime energy region of experimental measurement. [ABSTRACT FROM AUTHOR]

Fully relativistic (four-component) density-functional theory calculations were performed for intermetallic dimers MM′, where M=Ge, Sn, Pb, and element 114, and M′=group 10 elements (Ni, Pd, and Pt) and group 11 elements (Cu, Ag, and Au). PbM and 114M, where M are group 14 elements, were also considered. The results have shown that trends in spectroscopic properties—atomization energies De, vibrational frequencies ωe, and bond lengths Re, as a function of M′, are similar for compounds of Ge, Sn, Pb, and element 114, except for De of PbNi and 114Ni. They were shown to be determined by trends in the energies and space distribution of the valence ns(M′) atomic orbitals (AOs). According to the results, element 114 should form the weakest bonding with Ni and Ag, while the strongest with Pt due to the largest involvement of the 5d(Pt) AOs. In turn, trends in the spectroscopic properties of MM′ as a function of M were shown to be determined by the behavior of the np1/2(M) AOs. Overall, De of the element 114 dimers are about 1 eV smaller and Re are about 0.2 a.u. larger than those of the corresponding Pb compounds. Such a decrease in bonding of the element 114 dimers is caused by the large SO splitting of the 7p orbitals and a decreasing contribution of the relativistically stabilized 7p1/2(114) AO. On the basis of the calculated De for the dimers, adsorption enthalpies of element 114 on the corresponding metal surfaces were estimated: They were shown to be about 100–150 kJ/mol smaller than those of Pb. [ABSTRACT FROM AUTHOR]

Fully relativistic four-component density functional theory with the general gradient approximation calculations have been performed to determine the adsorption energy and position of the superheavy element 112 on a Au surface. Extended cluster as well as embedded cluster calculations were used to simulate the surface which allow for the top, bridge, and hollow adsorption sites without losing the advantage of symmetry considerations. Comparison with analogous calculations of the adsorption of the homologue element Hg allows to predict the adsorption of element 112 at a bridge site with a binding energy of 0.67 eV. [ABSTRACT FROM AUTHOR]

The influence of relativistic effects on properties and volatility of the group-8 tetroxides MO4, where M=Ru, Os, and element 108, Hs, was studied on the basis of results of the fully relativistic (four component) and nonrelativistic density functional theory calculations. Relativistic effects were shown to increase bond strengths and decrease bond lengths in these molecules. They are responsible for a decrease in molecular polarizabilities and an increase in ionization potentials. The effects are much stronger in HsO4 than in the lighter congeners. Relativistic effects were also shown to slightly decrease dispersion interaction energies of RuO4, OsO4, and HsO4 with an inert (quartz or silicon nitride) surface, i.e., they increase volatility of these compounds as studied in the “one-atom-at-a-time” gas-phase chromatography experiments. They do, however, not influence the trend in group 8: both relativistically and nonrelativistically, volatility should change as RuO444. The reason for that is identical trends in the relativistic and nonrelativistic space distributions of the valence d electrons. [ABSTRACT FROM AUTHOR]

Large multiconfiguration Dirac–Fock calculations were performed for all neutral and up to 7 and 8 times ionized species of elements 107 and 108, respectively, as well as all the homologous elements Mn, Tc, Re, Fe, Ru, and Os for a number of different total angular momenta. Comparison of the resulting ionization potentials to the known values of the homologues allow an extrapolation and thus a prediction of the chemically important seven or eight ionization potentials of elements 107 or 108 as well as a prediction of some ionic radii. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

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 MCl5 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 of the metals for electronic configurations obtained as a result of the molecular calculations and their overlap with ligands show opposite trends in behavior for ns1/2, np1/2, and (n-1)d5/2 orbitals for Ta and Ha in the relativistic and nonrelativistic cases. Relativistic contraction and energetic stabilization of the ns1/2 and np1/2 wave functions and expansion and destabilization of the (n-1)d5/2 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 MCl5 molecules in going from Nb to Ha making element Ha an analog of V. 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. [ABSTRACT FROM AUTHOR]

Multiconfiguration relativistic Dirac–Fock (MCDF) values have been computed for the first four ionization potentials (IPs) of element 104 (unnilquadium) and of the other group 4 elements (Ti, Zr, and Hf). Factors were calculated that allowed correction of the systematic errors between the MCDF IPs and the experimental IPs. Single ‘‘experimental’’ IPs evaluated in eV (to ±0.1 eV) for element 104 are: [104(0),6.5]; [104(1+),14.8]; [104(2+),23.8]; [104(3+),31.9]. Multiple experimental IPs evaluated in eV for element 104 are: [(0-2+),21.2±0.2]; [(0-3+),45.1±0.2]; [(0-4+),76.8±0.3]. Our MCDF results track 11 of the 12 experimental single IPs studied for group 4 atoms and ions. The exception is Hf(2+). We submit our calculated IP of 22.4±0.2 eV as much more accurate than the value of 23.3 eV derived from experiment. [ABSTRACT FROM AUTHOR]

It is found that the electric dipole polarizabilities of neutral atoms correlate very strongly with their first ionization potential within the groups of elements with the same angular momenta of the outermost electrons. As the latter values are known very accurately, this allows a very good (<30%) prediction of various atomic polarizabilities. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Fully relativistic density functional calculations have been performed for group 8 tetroxides MO[sub 4], where M=Ru, Os, and element 108, Hs. The electronic structure analysis has shown HsO[sub 4] to be very similar to OsO[sub 4], with the covalence and stability increasing from OsO[sub 4] to HsO[sub 4]. Using models of atom-slab interactions, adsorption enthalpies of RuO[sub 4] and HsO[sub 4] on the quartz surface have been calculated using some models of physisorption. The volatility of the single species was shown to have the following trend, RuO[sub 4]4≤HsO4, with differences in the adsorption enthalpies between the species being almost within the experimental uncertainty of ±1.5 kJ/mol. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We reply to the comment on our paper "Four-component relativistic density functional calculations of heavy diatomic molecules" [J. Chem. Phys. 112, 3499 (2000)] in which the values of our calculated spectroscopic constants for heavy diatomic molecules were reinvestigated. We point out that the improved spectroscopic constants presented by Liu and van Wu¨llen confirm our basic conclusion that the generalized gradient approximations tend to overcorrect errors of the bond lengths calculated by the local density approximation for molecules with heavy constituents. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We perform accurate four-component calculations for heavy closed-shell diatomic molecules in the framework of relativistic density functional theory using local and gradient corrected density functional schemes. As examples we have chosen Cu[sub 2], Ag[sub 2], Au[sub 2], Tl[sub 2], Pb[sub 2], Bi[sub 2], and Pt[sub 2]. The potential energy curves show the quality, and the discrepancies of the density functionals unscreened from any approximation of the relativistic effects. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Effect of strongly coupled plasma on the excitation energies and transition probabilities for the respective transitions 1s2:1Se → 1sns:3Se (n = 2, 3, 4) and 1s2:1Se → 1snp:3Po (n = 2, 3, 4) allowed by magnetic dipolar and quadrupolar excitations have been analyzed for the first time for the two-electron ions C4+, O6+, Ne8+, Mg10+, Si12+, and S14+. Time dependent Hatree-Fock theory within variational approach has been adopted for such a study. The effect of surrounding plasma has been treated through the standard Ion-Sphere (IS) model of the plasma where the plasma density is varied systematically from a low value to a pretty high value such that the respective excited states go over to continuum due to such a confinement. The effect of external pressure generated due to plasma confinement on the estimated spectral properties has been analyzed systematically. [ABSTRACT FROM AUTHOR]