Page 64 - Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)

IR-11.5 S O L I D S

Key aspects of the Kro ¨ger–Vink point defect notation are summarized in Table IR-11.1.

a

Table IR-11.1 Examples of defect notation in M 2þ (X ) 2 containing a f oreign ion Q
x
interstitial M 2þ ion M * i * M a tom vacancy V M
interstitial X ion X 0 i X a tom vacancy V X x

x
M 2þ ion vacancy V M normal M 2þ ion M M
00
–
–
X ion vacancy V X * normal X ion X X x
*
interstitial M a tom M x i Q 3þ ion at M 2þ site Q M
x
interstitial X a tom X x i Q 2þ ion at M 2þ site Q M
þ
0
interstitial M ion M * i Q ion at M 2þ site Q M
þ
M ion vacancy V M free electron e 0
0
þ
free hole h *
a 2þ
Consider an ionic compound M (X ) 2 . T he formal charge on M i s 2 þ, t he formal
charge on X i s 1 . I f a n a tom X i s r emoved, one negative unit of charge remains on
the vacant X s ite. The vacancy is neutral with respect to the ideal MX 2 lattice and is
therefore indicated by V X or V X . x I f t he electron is also removed from this site, the
resultant vacancy is effectively positive, i.e. V X . * S imilarly, removal of an M a tom
þ
0
leaves V M , r emoval of an M ion leaves V M , r emoval of an M 2þ ion leaves V M . I f a n
00
impurity with a f ormal charge of three positive units Q 3þ is substituted on the M 2þ
*
site, its effective charge is one positive unit. Therefore it is indicated by Q M .
IR-11.4.5 Defect clusters a nd use of quasi-chemical equations
Pairs or more complicated clusters of defects can be present in a s olid. Such a d efect cluster
is indicated between p arentheses. The e ffective charge of the cluster is indicated as an upper
right index.
Examples:
0 x
*
1. ðCa V Þ denotes a n eutral defect pair in a s olid solution, for example o f C aCl 2
K K
in KCl.
0
2. ðV V Þ or ðV Pb V Cl Þ indicates a c harged vacancy pair in PbCl 2 .
00
* 0
Pb Cl
Quasi-chemical reactions may be written for the formation of such defect clusters.
Examples:
3. Cr * Mg þ V Mg ! ð Cr Mg V Mg Þ describes the association reaction of a C r 3þ impurity in
00
0
MgO with magnesium vacancies.
x
4. 2Cr * þ V 00 ! ð Cr Mg V Mg Cr Mg Þ gives another possible association reaction in the
Mg Mg
system of Example 3.
x
5. Gd * Ca þ F ! 0 i ð Gd Ca F i Þ describes the formation of a d ipole between a G d 3þ
impurity a nd a fl uorine interstitial in CaF 2 .
IR-11.5 P H A S E N O M E N C L A T U R E
IR-11.5.1 Introduction
7
The use o f t he Pearson notation (see also Section IR-3.4.4) is recommended for the
designation of the structures o f m etals a nd solid solutions in binary and more complex

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