EPRI EF Nuclear Power Plant Materials Certification Practice Test

Regular, repeating arrangement of atoms in a solid is described by a lattice. In crystalline solids, atoms occupy positions that repeat in three dimensions, forming a crystal lattice that can be described by a unit cell and lattice parameters. This translational symmetry is what gives crystals their predictable structure and properties, such as characteristic diffraction patterns. The other terms refer to different ideas: strain is deformation under stress, pores are voids in the material, and shrinkage cavities are defects formed during solidification, not the orderly, periodic framework of atoms.