The two-dimensional melting behaviour of the inverse-twelfth-power sys
tem and its dependence on boundary and initial conditions has been re-
examined with long molecular dynamics simulation runs. The system cons
ists of 1225 particles, which in a first series of runs is being simul
ated under standard periodic boundary conditions. It is feasible to re
concile some central simulation results with the experimental data of
Murray et al., 1987, Phys. Rev. Lett., 58, 1200 for possible two-stage
melting of submicron-sized charged colloidal spheres in liquid water.
In another series of simulations, the particles are confined to a rou
ghly rectangular cell with irregularly shaped walls. The energy as a f
unction of density is found to be very sensitive to the choice of boun
dary conditions. The dependence on the initial conditions is studied b
y setting up the latter simulations with different sets of starting co
ordinates-some of them probably those of a hexatic phase-which were di
rectly obtained from Murray et al.'s experimental data for colloidal s
uspensions. Using the short ranged r-12 potential, molecular dynamics
simulations of these configurations were examined over five million ti
me steps each. The initial order, even if experimentally found to be c
onsistent with that of a hexatic phase, is not seen to undergo any rap
id breakup. This suggests that kinetic bottlenecks limiting equilibrat
ion are still important, even for runs of this length.