  In the upcoming process to overcome the limitations of the standard von
Neumann architecture, synaptic electronics is gaining a primary role for the
development of in-memory computing. In this field, Ge-based compounds have been
proposed as switching materials for nonvolatile memory devices and for
selectors. By employing the classical molecular dynamics, we study the
structural features of both the liquid states at 1500K and the amorphous phase
at 300K of Ge-rich and Se-rich chalcogenides binary GexSe1-x systems in the
range x 0.4-0.6. The simulations rely on a model of interatomic potentials
where ions interact through steric repulsion, as well as Coulomb and
charge-dipole interactions given by the large electronic polarizability of Se
ions. Our results indicate the formation of temperature-dependent hierarchical
structures with short-range local orders and medium-range structures, which
vary with the Ge content. Our work demonstrates that nanosecond-long
simulations, not accessible via ab initio techniques, are required to obtain a
realistic amorphous phase from the melt. Our classical molecular dynamics
simulations are able to describe the profound structural differences between
the melt and the glassy structures of GeSe chalcogenides. These results open to
the understanding of the interplay between chemical composition, atomic
structure, and electrical properties in switching materials.
