  For two-dimensional many-particle systems first-order, second-order, single
step continuous, as well as two-step continuous (KTHNY-like) melting
transitions have been found in previous studies. Recent computer simulations,
using particle numbers in the $\geq 10^5$ range, as well as a few experimental
studies, tend to support the two-step scenario, where the solid and liquid
phases are separated by a third, so called hexatic phase. We have performed
molecular dynamics simulations on Yukawa (Debye-H\"uckel) systems at conditions
earlier predicted to belong to the hexatic phase. Our simulation studies on the
time needed for the equilibration of the systems conclude that the hexatic
phase is metastable and disappears in the limit of long times. We also show
that simply increasing the particle number in particle simulations does not
necessarily result in more accurate conclusions regarding the existence of the
hexatic phase. The increase of the system size has to be accompanied with the
increase of the simulation time to ensure properly thermalized conditions.
