Notation for description of point defects

In the development of the field of defect chemistry of inorganic compounds various systems of notation have been proposed and used to describe point defects. However, the most widely adopted system is that due to Kroger and Vink (1956) (see also Kroger (1964)), and this will be used in this book. This system describes crystals in terms of structural elements, and an imperfection is indicated by a major symbol describing its chemical content and a subscript that indicates the site that it occupies. 

In an oxide the metal ions on the regular lattice positions are written Mm, where the subscript thus describes the type of lattice site which is occupied. Correspondingly, the oxygen ions on normal lattice sites are written Oq. 

The native point defects in an oxide include M and O vacancies and M and O interstitial atoms or ions. Vacancies are denoted by v with a subscript M or O referring to vacant metal or oxygen sites, respectively. Interstitial ions or sites are described with a subscript i . Vacancies and interstitials in an oxide are thus written 

Correspondingly, an imoccupied or vacant interstitial site can be written Vi. 

While the notation traditionally has used V for vacancy, confusion with the element vanadium (V) can be avoided by using lower-case v or italic V. Here, we will use the lower case v. 

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