Question

Which point defect lowers the density of a crystal?

Answer 1

1. The point defect that lowers the density of a crystal is the Schottky defect.
2. These ions are completely removed from the crystal lattice (often to the surface), resulting in a loss of mass.
3. In a Schottky defect, an equal number of cations and anions are missing from their regular lattice sites, creating vacancies in the crystal structure.
   1. Since ions are missing, the mass of the crystal decreases.
   2. The volume remains nearly the same.
   3. As a result, density = `("mass"/"volume")`, the overall density of the crystal decreases.