nearatomic

Nearatomic is an informal term used in science to describe quantities, structures, or phenomena that are close to the atomic scale but not quite at the scale of a single atom. There is no universally accepted formal definition, and its precise meaning varies by discipline. In practice, nearatomic refers to length scales roughly from tens of picometers to a few nanometers (about 0.1–5 nm), corresponding to a handful of atoms across.

In imaging and characterization, nearatomic resolution describes measurements or images that approach the size of an individual atom, typically on the order of 1 ångström (0.1 nm) or slightly larger, obtainable with high-resolution transmission electron microscopy or scanning probe techniques. In materials science, near-atomic thickness or layering means a film only a few atomic layers thick, where quantum confinement and surface effects are pronounced. In chemistry and nanocluster science, nearatomic assemblies denote small aggregates of atoms or molecules where discrete size-dependent properties emerge, rather than bulk behavior.

The term is largely contextual and its use signals proximity to atomic-scale models while acknowledging that exact single-atom precision is not assumed. Researchers use it to denote regimes where atomistic descriptions are appropriate but where instrumentation or thermal fluctuations limit exact measurements.

See also: atomic scale, nanometer, angstrom, scanning probe microscopy, cryo-electron microscopy.