Ab-Initio Calculation of the Metal-Insulator Transition in Sodium rings and chains and in mixed Sodium-Lithium systems

We study how the Mott metal-insulator transition (MIT) is influenced when we deal with electrons with different angular momenta. For lithium we found an essential effect when we include $p$-orbitals in the description of the Hilbert space. We apply quantum-chemical methods to sodium rings and chains in order to investigate the analogue of a MIT, and how it is influenced by periodic and open boundaries. By changing the interatomic distance we analyse the character of the many-body wavefunction and the charge gap. In the second part we mimic a behaviour found in the ionic Hubbard model, where a transition from a band to a Mott insulator occurs. For that purpose we perform calculations for mixed sodium-lithium rings. In addition, we examine the question of bond alternation for the pure sodium system and the mixed sodium-lithium system, in order to determine under which conditions a Peierls distortion occurs.Comment: 8 pages, 7 figures, accepted Eur. J. Phys.

DESIGN OF A USER CHARGE FOR HEAVY-DUTY VEHICLES ON GERMAN MOTORWAYS CONSIDERING THE OBJECTIVES OF EFFICIENCY, FAIRNESS AND ENVIRONMENTAL PROTECTION

The German government plans to introduce a kilometre charge on motorways for heavy duty vehicles "12t, beginning in the year 2003. According to an EU Directive the charge has to be orientated to the average infrastructure costs and can be differentiated according to the environmental performance (“EURO Standard”) of the vehicles. Based on the possible differentiation of the user charge this paper analyses the probable impacts on the transport market and on basic environmental indicators. Three scenarios are constructed: first, a modest user charge only on motorways; second, a higher user charge on the whole network of federal roads with a given level of service of the railways; and third, the previous scenario combined with an improved level of service of the railways. The result is that only in the case of the third scenario the hope of environmental policy is realistic that road transport can be reduced and environmental quality significantly improved through a road user charging scheme. Document type: Articl

On the ground state of solids with strong electron correlations

We formulate the calculation of the ground-state wavefunction and energy of a system of strongly correlated electrons in terms of scattering matrices. A hierarchy of approximations is introduced which results in an incremental expansion of the energy. The present approach generalizes previous work designed for weakly correlated electronic systems.Comment: 17 pages, Latex(revtex

Correlation effects in MgO and CaO: Cohesive energies and lattice constants

A recently proposed computational scheme based on local increments has been applied to the calculation of correlation contributions to the cohesive energy of the CaO crystal. Using ab-initio quantum chemical methods for evaluating individual increments, we obtain 80% of the difference between the experimental and Hartree-Fock cohesive energies. Lattice constants corrected for correlation effects deviate by less than 1% from experimental values, in the case of MgO and CaO.Comment: LaTeX, 4 figure

Correlation effects in ionic crystals: I. The cohesive energy of MgO

High-level quantum-chemical calculations, using the coupled-cluster approach and extended one-particle basis sets, have been performed for (Mg2+)n (O2-)m clusters embedded in a Madelung potential. The results of these calculations are used for setting up an incremental expansion for the correlation energy of bulk MgO. This way, 96% of the experimental cohesive energy of the MgO crystal is recovered. It is shown that only 60% of the correlation contribution to the cohesive energy is of intra-ionic origin, the remaining part being caused by van der Waals-like inter-ionic excitations.Comment: LaTeX, 20 pages, no figure

Spectroscopija 125Te (n,γ), (d,p) i (3He,α) reakcijama

Single γ-ray spectra and γγ-coincidences, following thermal neutron capture in 124Te, were measured with semiconductor detectors at the light-water reactor LWR - 15 at Řež. Intensities of g transitions in 125Te were normalized using the absolute intensity of 7.8% of the 6620 keV line in 36Cl. The high resolution (d,p) measurements were performed with 17 MeV deuterons, using the Q3D spectrograph at two scattering angles of 15° and 30°. Spectra were recorded in the range up to 3.3 MeV and calibrated using the proton peaks with l =1, and the corresponding level energies were determined in the thermal neutron capture reaction. The (3He,α) experiment was carried out with a 32 MeV He beam at the angle of 10°. The spectrum was recorded in one run by means of a large detector in a range up to approximately 4.7 MeV. The absolute intensities were determined by measuring the total beam current.Mjerili su se izravni γ- i sudesni γ-γ-spektri nakon uhvata termičkih neutrona u 124Te. Mjerenja (d,p) reakcija visokog razlučivanja na toj jezgri izvela su se s deuteronima 17 MeV na kutovima od 15° i 30° , pomoću Q3D spektrografa. Također se mjerio spektar u reakciji (3He,α) na 10° . Na osnovi tih mjerenja utvrđena su mnoga nova stanja 125Te na energijama uzbude do oko 4.5 MeV. Razlika grananja 403/443 keV iz izravnih i sudesnih γ-spektara ukazuje na jaku primjesu E2 u primarnom prijelazu od 6125 keV

Cohesive properties of alkali halides

We calculate cohesive properties of LiF, NaF, KF, LiCl, NaCl, and KCl with ab-initio quantum chemical methods. The coupled-cluster approach is used to correct the Hartree-Fock crystal results for correlations and to systematically improve cohesive energies, lattice constants and bulk moduli. After inclusion of correlations, we recover 95-98 % of the total cohesive energies. The lattice constants deviate from experiment by at most 1.1 %, bulk moduli by at most 8 %. We also find good agreement for spectroscopic properties of the corresponding diatomic molecules.Comment: LaTeX, 10 pages, 1 figure, accepted by Phys. Rev.

Investigation of the Properties of Galactic Cosmic Rays with the KASCADE-Grande Experiment

The properties of galactic cosmic rays are investigated with the KASCADE-Grande experiment in the energy range between $10^{14}$ and $10^{18}$ eV. Recent results are discussed. They concern mainly the all-particle energy spectrum and the elemental composition of cosmic rays.Comment: Proc. RICAP 09, Nucl. Instr. and Meth. in pres