The standard Pauli Hamiltonian is highly singular for Coulomb potentials near the nuclei of the atoms. It is shown that the theory of effective Hamiltonians allows the determination of Pauli-like Hamiltonians that are regular enough to be used in variational calculations. A numerical illustration is given for hydrogenic atoms with atomic number varying from Z = 1 to Z = 86. These calculations yield relativistic correction potentials which are used for studying the series of neutral rare gas atoms. Our approach opens the way for accurate two-component calculations for molecules.

Electronic and structural properties of energetically low-lying isomers of isolated Ti x O y (x = 1-6, y = 1-12) molecular systems have been investigated by density functional theoretical methods. A variety of stationary points are thoroughly characterized. We report total cluster energies, equilibrium geometries and harmonic vibrational wavenumbers.

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With the application of voltage pulses, mounds of 20 nm in diameter and 2 nm in height on the average can be created on a gold surface with very high efficiency in nonconducting liquid from a gold tip. The created mounds are similar to those produced in air. Tungsten and PtIr tips are also used in this study and the dominant shapes of created structures are craters and volcanolike mounds, respectively. Our data show that these nanometer structures are created by a mechanical contact between the tip and the sample.