latticesite

A lattice site, sometimes written latticesite, is a defined position in a crystal lattice that can be occupied by an atom, an ion, or left vacant. In a perfect crystal, lattice sites form a regular three-dimensional network determined by the crystal structure. The concept is central to solid-state chemistry and materials science, where site occupancy helps describe the arrangement of atoms and the presence of defects.

Lattice sites can be classified by occupancy. Substitutional sites are lattice positions normally occupied by host atoms that may be taken by impurity atoms of a different element. Interstitial sites are smaller spaces between lattice points that can accommodate atoms without displacing the host atoms; in close-packed structures, common interstitial sites are octahedral and tetrahedral. A vacancy is the absence of an atom at a lattice site, a fundamental defect that enables many diffusion and mass-transport processes.

The distribution and occupancy of lattice sites influence material properties. Diffusion often proceeds by atoms jumping from one lattice site to a neighboring vacancy (the vacancy mechanism) or by movement through interstitial sites (the interstitial mechanism). Substitutional impurities and vacancies also affect electrical conductivity, mechanical strength, and diffusion coefficients. In semiconductors and ceramics, dopants frequently occupy specific lattice sites to tailor electronic structure and ionic conductivity.

Characterization methods such as X-ray and neutron diffraction, electron microscopy, and atom probe tomography are used to determine site occupancy and defect concentrations. The lattice-site framework provides a basis for understanding defects, diffusion behavior, phase stability, and dopant interactions in crystalline solids.