Interstitialatomen

Interstitialatomen are atoms that occupy the spaces between the regular lattice points in a crystal, rather than substituting for host atoms. They are typically smaller than the host atoms and can fit into voids created by the arrangement of the lattice.

In close-packed crystal structures such as face-centered cubic (fcc) and hexagonal close-packed (hcp) lattices, common interstitial sites are octahedral and tetrahedral voids. In body-centered lattices, smaller atoms may occupy available interstitial positions with varying ease. The ability of an atom to be an interstitial solute depends on its size relative to the host atoms and the energetics of the lattice.

Interstitial atoms are introduced through alloying, diffusion, irradiation, or during rapid solidification. Their movement within the lattice—interstitial diffusion—often occurs via hopping between neighboring interstitial sites and generally has lower energy barriers than substitutional diffusion, making them important for processes such as carburization, nitriding, and hydrogen transport.

The presence of interstitial atoms distorts the lattice, affecting mechanical and physical properties. They can strengthen a material by hindering dislocation motion (solid-solution strengthening) and modify diffusion rates and phase stability. Excess interstitials may lead to problems such as embrittlement or hydride formation, depending on the system.

Common examples include carbon in iron (carbonate and alloy steels), nitrogen in steel, and hydrogen in many metals, where interstitials dramatically influence hardness, strength, and ductility. In semiconductors, interstitials also affect defect chemistry and dopant diffusion, impacting device performance.