Wolf-Dieter Sepp

All-electron Dirac—Fock—Slater SCF calculations of the Au2 molecule

Abstract All-electron Dirac—Fock—Slater SCF clculations of the Au 2 molecule have been carried out using relativistic numerical atomic basis functions. In order to get a numerically accurate potential energy curve an improved calculation of the direct Coulomb potential has been taken into account. The relativistic effect inthe binding energy, the bond distance and the vibration frequency of the ground state potential energy curve have been studied in comparison with consistent non-relativistic results.

Relativistic effects in physics and chemistry of element 105. II. Electronic structure and properties of group 5 elements bromides

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.

Relativistic effects in physics and chemistry of element 105. III. Electronic structure of hahnium oxyhalides as analogs of group 5 elements oxyhalides

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.

Relativistic effects in physics and chemistry of element 105. I. Periodicities in properties of group 5 elements. Electronic structure of the pentachlorides

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.

A new version of the program TSYM generating relativistic molecular symmetry orbitals for finite double point groups

A revised and extended version of the program TSYM is presented. Relativistic symmetry-adapted basis systems for molecular calculations are constructed from atomic orbitals according to the LCAO method. The molecular symmetry group can be one of 45 finite double point groups. The algorithm based on the projection operator formalism automatically ensures the linear independence of the symmetry orbitals. Time reversal invariance, taken into account as an additional symmetry property, provides further information on the structure of matrix elements.

COMPUTATION OF RELATIVISTIC SYMMETRY ORBITALS FOR FINITE DOUBLE POINT GROUPS

A program is presented for the construction of relativistic symmetry-adapted molecular basis functions. It is applicable to 36 finite double point groups. The algorithm, based on the projection operator method, automatically generates linearly independent basis sets. Time reversal invariance is included in the program, leading to additional selection rules in the non-re1ativistic limit.

Level energies and lifetimes in the 3p4 3d configuration of chlorine-like ions

Large-scale multiconfiguration Dirac-Fock wavefunctions have been used to study excitation energies and lifetimes of the 3s2 3p4 3d configuration in the chlorine isoelectronic sequence. We present an ab-initio calculation of all dipole allowed transitions from 3s2 3p4 3d to the 3s2 3p5 (J = 1/2, 3/2) ground state levels for 6 ions in the atomic range 18 ≤ Z ≤ 41. To generate the wavefunctions we used the active-space method outside a closed 1s2 2s2 2p6 core. Our study incorporates the major correlation effects by including all virtual single, double and triple excitations into the 3l subshells as well as all singles and doubles into 4l. Excitations into the 4l and higher subshells do not contribute so much to the transition energies, but they clearly affect the transition probabilities and lifetimes. Additionally, the rearrangement of the electron density during the spontaneous emission is taken into account by a separate optimization of the wavefunctions in the 3p4 3d and 3p5 configurations. This often reduces the deviations between the lifetimes in different gauge forms, in particular at the neutral end of the isoelectronic sequence. Comparison is made with previous calculations and available experimental data. We conclude that the accuracy of the presented excitation energies (apart from Ar II) has been improved to about 5000 cm−1 for higher charged ions, i.e. by about a factor of 2 or so with respect to recent computations.

Relativistic many-electron SCF correlation diagram for superheavy quasimolecules: PbPb☆

Abstract We present the first relativistic many-electron SCF correlation diagram for a superheavy quasimolecule: PbPb. The discussion shows a large number of quantitative as well as qualitative differences as compared with the known one-electron correlation diagram.

Total differential scattering cross section of Ar+-Ar at 15 to 400 keV

Abstract We report on the measurement of the total differential scattering cross section of Ar+-Ar at laboratory energies between 15 and 400 keV. Using an ab initio relativistic molecular program which calculates the interatomic potential energy curve with high accuracy, we are able to reproduce the detailed structure found in the experiment.

Evidence for an additional coupling of the innermost shells in very heavy quasi-molecular ion-atom collisions

Due to the tremendous spin-orbit splitting of quasi-molecular levels of super-heavy collision systems (Z=Z1+Z2<or=137) bombarding energy 0.5-6 MeV N-1, unusual couplings may occur around Z approximately=165. Experimental evidence for such a theoretically predicted coupling is discussed.