  We discuss the problem of partitioning a macroscopic system into a collection
of independent subsystems. The partitioning of a system into replica-like
subsystems is nowadays a subject of major interest in several field of
theoretical and applied physics, and the thermodynamic approach currently
favoured by practitioners is based on a phenomenological definition of an
interface energy associated with the partition, due to a lack of easily
computable expressions for a microscopic (i.e.~particle-based) interface
energy. In this article, we outline a general approach to derive sharp and
computable bounds for the interface free energy in terms of microscopic
statistical quantities. We discuss potential applications in nanothermodynamics
and outline possible future directions.
