Where Bulk Physics Ends: Pairwise vs Many-Body Bonding in a Metal Nanocluster

Nanophilosophy asks a concrete question long before it asks an abstract one: at what point does a handful of atoms start behaving like "a material" at all? This simulator builds a real FCC gold nanocluster atom by atom and evaluates its cohesion under two genuinely different physical models — a pairwise Lennard-Jones potential and the many-body Gupta (second-moment tight-binding) potential used in real nanocluster research — calibrated to agree exactly at full bulk coordination. Grow the cluster, extend the interaction cutoff, and watch surface atoms light up where the two models disagree: a direct, numerical demonstration that "the" cohesive energy of a nanoscale object is coordination- and size-dependent, and that which model you choose to trust is itself an epistemic decision with a measurable cost.