Interatomic

Interatomic refers to interactions and forces that occur between atoms. These forces arise from electromagnetic interactions among atomic nuclei and electrons and are described by potential energy surfaces within quantum mechanical frameworks, such as the Born–Oppenheimer approximation. The pattern and strength of interatomic interactions determine the structure and behavior of matter at the atomic scale, including the formation of bonds and the arrangement of atoms in solids.

The core types of interatomic interactions include covalent, ionic, and metallic bonding, as well as van der Waals forces (dispersion and dipole-induced dipole interactions). Hydrogen bonding is a directional, relatively strong interaction often considered a special case of interatomic or intermolecular forces between electronegative atoms and hydrogen. The relative balance of these forces sets interatomic distances, bond strengths, and the geometry of molecules and crystal lattices.

Interatomic potentials are mathematical models used to describe energy as a function of atomic positions. Classical potentials such as Lennard-Jones, Morse, Stillinger–Weber, and embedded-atom methods are employed in simulations of materials and polymers, while ab initio methods compute forces from first principles based on electronic structure.

Interatomic interactions underpin material properties including elasticity, thermal conductivity, diffusion, phase stability, and vibrational behavior (phonons) in crystals. They also govern chemical bonding, reaction pathways, and molecular geometries. Experimental techniques such as X-ray and neutron diffraction, spectroscopy, and atomic force microscopy provide information about interatomic distances and forces, enabling the characterization of materials at the atomic scale.