Question

describe point defect balance with possible terms.

Answer 1

Point defects are unavoidably present on surfaces because of their high configurational entropy. There is a corresponding equilibrium intrinsic defect concentration at each temperature.

The defect formation may either occur internally in the solid or through reactions with the environment and hence the rules for formulating defect reactions are required. These rules comprise of electroneutrality and mass balance.

Mass balance:

The number and kinds of atoms involved in the defect reaction must be the same before and after the defect formation. Vacancies, which are represented by empty sites, have zero mass and do not count. The defect reaction must balance with respect to the mass.

Electroneutrality:

keeping the perfect crystal as reference, the total effective charge must remain same before and after the formation of the defect and crystal should be electrically neutral. Charges can be balanced either by effective charge or real charges and must be balance on both side of reaction.