  (Abridged) In this paper we present a compilation of results from our most
advanced neutron star merger simulations, including a description of the
employed numerical procedures and a more complete overview over a large number
of computed models. The three-dimensional hydrodynamic simulations were done
with a code based on the Piecewise Parabolic Method with up to five levels of
nested Cartesian grids. The simulations are basically Newtonian, but
gravitational-wave emission and the corresponding back-reaction are taken into
account. The use of a physical nuclear equation of state allows us to follow
the thermodynamic history of the stellar medium and to compute the energy and
lepton number loss due to the emission of neutrinos. The computed models differ
concerning the neutron star masses and mass ratios, the neutron star spins, the
numerical resolution expressed by the cell size of the finest grid and the
number of grid levels, and the calculation of the temperature from the solution
of the entropy equation instead of the energy equation. Our simulations show
that the details of the gravitational-wave emission are still sensitive to the
numerical resolution, even in our highest-quality calculations. The amount of
mass which can be ejected from neutron star mergers depends strongly on the
angular momentum of the system. Our results do not support the initial
conditions of temperature and proton-to-nucleon ratio assumed in recent work
for producing a solar r-process pattern for nuclei around and above the A
approx 130 peak. The improved models confirm our previous conclusion that
gamma-ray bursts are not powered by neutrino emission during the dynamical
phase of the merging of two neutron stars.
