A model, including the chemical details of core
nanoparticles as well as explicit surface charges and hydrophobic
patches, of triblock Janus particles is employed to simulate
nucleation and solid−solid phase transitions in two-dimensional
layers. An explicit solvent and a substrate are included in the
model, and hydrodynamic and many-body interactions were taken
into account within many-body dissipative particle dynamics
simulation. In order not to impose a mechanism a priori, we
performed free (unbiased) simulations, leaving the system the
freedom to choose its own pathways. In agreement with the
experiment and previous biased simulations, a two-step mechanism
for the nucleation of a kagome lattice from solution was detected. However, a distinct feature of the present unbiased versus biased
simulations is that multiple nuclei emerge from the solution; upon their growth, the aligned and misaligned facets at the grain
boundaries are introduced into the system. The liquid-like particles trapped between the neighboring nuclei connect them together.
A mismatch in the symmetry planes of neighboring nuclei hinders the growth of less stable (smaller) nuclei. Unification of such
nuclei at the grain boundaries of misaligned facets obeys a two-step mechanism: melting of the smaller nuclei, followed by
subsequent nucleation of liquid-like particles at the interface of bigger neighboring nuclei. Besides, multiple postcritical nuclei are
formed in the simulation box; the growth of some of which stops due to introduction of a strain in the system. Such an incomplete
nucleation/growth mechanism is in complete agreement with the recent experiments. The solid−solid (hexagonal-to-kagome) phase
transition, at weak superheatings, obeys a two-step mechanism: a slower step (formation of a liquid droplet), followed by a faster
step (nucleation of kagome from the liquid droplet).