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With the help of resolution of the identity (RI) a compact representation for the zeroth-order (ZORA) and infinite-order (IORA) regular approximation Hamiltonians in matrix form is developed. The new representation does not require calculation of any additional molecular integrals, which involve an auxiliary basis set used in the RI. The IORA computational scheme is modified in such a way that the erroneous gauge dependence of the total energy is reduced by an order of magnitude. The new quasi-relativistic method, dubbed IORAmm, is tested along with the ZORA and IORA methods in atomic and molecular calculations performed at the SCF and MP2 level. [Copyright &y& Elsevier]

A recently developed variationally stable quasi-relativistic method, which is based on the low-order approximation to the method of normalized elimination of the small component, was incorporated into density functional theory (DFT). The new method was tested for diatomic molecules involving Ag, Cd, Au, and Hg by calculating equilibrium bond lengths, vibrational frequencies, and dissociation energies. The method is easy to implement into standard quantum chemical programs and leads to accurate results for the benchmark systems studied. [Copyright &y& Elsevier]

Cosmic dust transports information about the composition and evolution of distant realms over space and time. Dust sources may be in our local neighbourhood, such as the surfaces of moons and small bodies, or further away, in the galactic environment. The interior of moons like Io or Enceladus are well known dust sources in our solar system. Dust grains are therefore like probes, giving us the opportunity to investigate these objects at a distance. Thus, a new field of activity has been born: Dust Astronomy. The ultimate tool for Dust Astronomy is a dust observatory which was never been flown so far. Until today, all our knowledge is based on smaller individual dust detectors flown on various interplanetary spacecraft. Recently, a new generation of dust telescopes, which can be combined to a full dust observatory, became available. The scientific goal of such an observatory is to characterise our micrometeoroid environment with high precision and sensitivity and to record an inventory of various dust populations from asteroidal, cometary and interstellar dust sources. Two competitive studies on a Dust Astronomy mission were performed as part of a master's course, including mission analysis and spacecraft design. The goal was to demonstrate the feasibility of an observatory reaching the main asteroid belt with a minimum spacecraft mass using electric propulsion. Additional secondary payloads supporting the primary objective were selected as well. The results prove that small probes with less than 700 kg mass are capable of placing an array of dust telescopes deep in the asteroid belt, leading to a huge leap in Dust Astronomy and our knowledge about the local dust environment. • First presentation of feasibility studies for a dust observatory between Earth and asteroid belt. • A dust observatory is a tool for dust astronomy and studies interplanetary and interstellar dust fluxes in our solar system. • The observatories reach the asteroid belt within 7 years using electric propulsion. • Two full mission studies were performed by a small satellite project. [ABSTRACT FROM AUTHOR]