  As an extension of the former study on 2-dimensional systems, we simulate
phase behavior of polymer-grafted colloidal particles in 3 dimensions by
molecular Monte Carlo technique in the canonical ensemble. We use a spherically
symmetric square-step repulsive interaction potential, which has been obtained
using self-consistent field calculation. In previous articles, we have studied
these model colloids in 2 dimensions and found that these particles, although
their interaction is purely repulsive, self-assemble into a string-like
assembly, in a narrow region of physical parameter sets. In the present work,
we show the existence of the string-like assembly in 3-dimensional systems and
study the statistical properties of the arrangement of these strings. The
average string length diverges around the region where the melting transition
line and the percolation transition line cross, which has also been found in 2
dimensions.
