Point defect monovacancy

A point defect refers to a localized defect (such as a monovacancy) or impurity (such as interstitial O). This includes any relaxation and/or distortion of the crystal around it. Many point defects are now ratlier well understood, especially in Si, tlranks to a combination of experiments providing infonnation of microscopic nature... 

From the fact that the structure of hexamethylethane is close-packed, we may infer that the point defects responsible for the translational motion of the molecules are monovacancies. The data indicate an overexponential increase in diffusivity with temperature near Tm, analogous to some observations made on inorganic crystals. Various explanations could be given for this increase such as anharmonicity of the... 

One of the major controversies in solid-state science is the nature of the dominant native point defect in silicon. Is the dominant native point defect in silicon the monovacancy or the silicon self-interstitial Well-developed arguments have been proposed for each type, but the current consensus is that both types are present and important. 

Monovacancy. Statistical thermodynamics requires that if a vacancy is formed by removing an atom from the crystal and depositing it on the surface, then the free energy of the crystal must decrease as the number of created vacancies increases until a minimum in this free energy is reached. Because a minimum in the free energy exists for a certain vacancy concentration in the crystal, the vacancy is a stable point defect. The following facts about vacancies have been obtained experimentally (12). 

---