The coalescence of two nanoparticles
is a fundamental process that
plays a dominant role in the formation of new nanoparticles. It constitutes
a direct way to synthesize bimetallic nanoparticles with the continuous
growth of potential applications. However, a full mechanistic comprehension
that will allow us to predict and control the coalescence result has
not been achieved yet. Probably, the main reason for this is the complexity
of the whole process, which brings together several elementary subprocesses
like segregation, surface reduction, structural stress, or even changes
of ordered states, which present a large complexity by themselves.
It is particularly important for computer simulations to consider
the fact that the mixing or segregation of components occurs trough
many diffusion events, which constitute rare events. These processes
require advanced methods to accelerate their sampling. In the present
work, we use well-tempered metadynamic simulations to describe the
thermodynamics of the coalescence of Au42 and Co13 clusters at different temperatures. We show several free-energy,
entropy, and enthalpy profiles and discuss in detail their particular
features. We also propose to rationalize the observed behavior in
terms of the calorimetric curves of the product and the reactant nanoparticles
involved.