Defects of a crystal lattice

In a lattice of an ideal crystal atoms (ions) settle down in space strictly is ordered and naturally, and электроны should be at levels with the minimal energy. In real crystals there are various distortions or infringements of this ideal arrangement of particles, which usually name by defects of a crystal lattice.

The nature of defects can be various and reaches from microlevel (electronic, nuclear) up to defects in microvolumes of substance. Depending on the size of that area disorder (area of distortions of a lattice), which is borrowed (occupied) by(with) those or other defects, they can be classified to an only geometrical attribute - "dimensions" of defect ("dimension" - number of measurements, on which the defect has macroscopic extent). On this classification the defects of a crystal lattice divide (share) on zero-dementional (dot), one, two and three-dimensional. Zero-dementional defects as a first approximation borrow (occupy) in a crystal area of distortions, commensurable on all directions with the size of atom or electron. The one-dimensional defects have extent considerably superior the size of atoms in any one direction (in other directions they zero-dementional), two demensions- in two and three-dimensional - in three directions.

Zero and the one-dimensional defects concern to microdefects or to defects of thin structure of a crystal. Zero-dementional the defects can be divided (shared) on electronic and nuclear. To electronic defects belong superfluous electrons, hole and exitons. To atomic zero-dementional to defects (fig. 9) the vacancies, impurity atoms replacing own atoms of substance in their regular rule (in lattice site), and own or impurity atoms which are taking place (displaced by) in irregular position irregular a rule(situation) in interstitial site of a lattice (of a particle, taking place in interstitial site, sometimes name interstitial site or interstitial). To one-dimensional nuclear defects concern regional and screw dislocation.

Two and the three-dimensional defects belong to macrodefects or defects of rough structure. Examples two demensions of defects are so-called mosaic structure of crystals, border of grains, the defects of packing, three-dimensional -pore, crack in a crystal, inclusion in him(it) of other phase and other infringements of integrity of a crystal.

Fig. 9. Types nuclear нульмерных of defects:

1- vacancies; 2 - impurity atom in unit of a lattice; 3 - impurity atom in interstice

The large meaning (importance), which is given to study of defects of a crystal lattice in physics of a firm body, is caused by their huge influence on properties of crystal substances. Besides the defects render often decisive influence on such processes, as growth of crystals, mass transport (diffussion) in firm bodies determining kinetics such important in technology silicates and other refractory not metal materials of processes, as powder (solid) phase of reaction, sintering, recrystallization and e. c.

As it was already marked, to nuclear zero measure or dot defects the vacancies, impurity atoms in regular units concern lattices and impurity atoms, dislocated in interstice. These the types of defects basically can meet in a lattice of crystals separately, but more often they are present at a combination with each other. Depending on it distinguish the following types nuclear zero measure of defects: firm solutions (switching defect nonstoichiometry), defects on Schottky and defects on Fraenkel