Interstitial formation

As the introduced cations are large, interstitial formation can be regarded as less likely, leaving anion vacancy formation ... 

Figure 2.4. Interstitial formation of a solid phase. The dissolution in the interstices of the structures of the metal (a) of the atoms of the gas (b) gives a solid solution (c) or an ordered phase (d).

Calculations of the fractional interstitialcy components for B, P, As, and Sb are shown in Table I (33, 39-42). A significant spread in the values of/, is obtained. The value of / has been correlated with the amount of energy required to make a substitutional dopant atom become interstitial. Energies of interstitial formation in Si are shown in Table II. The larger the energy... 

Table II. Estimated Interstitial Formation Energies in Silicon...

Some of the defect equilibria which we have deduced by this type of analysis were not surprising—a parent lattice may dissociate into interstitials and vacancies in conformity with appropriate equilibrium constants defects may associate, again consistent with an equilibrium constant or the lattice may dissolve excess atoms in simple solubility. (When we speak of a solvent or parent lattice we mean the crystallographic lattice, as it would be determined by x-ray analysis, stoichiometri-cally perfect, and free of vacancies or interstitials. We call the process of vacancy and interstitial formation lattice dissociation. Simple solution adds interstitials or fills voids in the parent lattice). 

The differences in the atom coordination around the interatomic cavities manifest themselves in the distribution of the interstitial formation energies. In LRC s as well as in crystals, the formation of dumbbell interstitial configurations is possible. The expressions for equilibrium concentrations of interstitials are similar to those given above for vacancies (6.19 and 20), with the difference, however, that one accounts in them for the difference of interstitial cavities and the possibility of dumbbell configuration formation. 

Note that in LRC, the stable Frenkel pairs may be formed (e.g., under irradiation). The energy spectrum of Frenkel pair formation is somewhat spread due to the spread in energies of vacancies and interstitials formation. The width of this spectrum as well as variations in energy of vacancies and interstitials formation may amount to some eV, and the typical values of the threshold energy of Frenkel pair formation in metallic glasses as well as in crystals may amount to about 25-30 eV. To point defects of a cluster one may attribute also the interstitial and substitutional impurities that locally break the topological and compositional order. 

Carbamoyl complexes from metal carbonyls and amines 5.8.2.12.4 Carbanions reactions with alkene complexes 5.8.2.3,4 metal carbonyls 5.8.2.S.5 Carbene complexes by alkene metathesis 5.8.2.3.11 formation 5.8.2.8.5 Carbides alkali metal formation 5.10.2.1 bonding 5.10.2 formation 5.10.2 industrial uses 5.10.2 interstitial formation 5.10.2 Carbometallacycle formation 5.S.2.2.2 Carbometallacycles from n-allyl complexes 5.S.2.3.9 Carbon reaction with alkali metals 5.10.2.1 Carbon dioxide complexes formation 5.8.2.14.1 Carbon monoxide displacement by alkenes 5.8.2.3.1 Carbonyl complexes by ligand exchange 5.8.2.12.2 from carbon monoxide 5.8.2.12.1, 5.8.2.12.2... 

The thermodynamic description of the formation of these defects is analogne to the description of vacancy-interstitial formation. 

Oxides that have a crystal structure that prefers interstitial formation have Frenkel and anti-Frenkel disorder and obey the following defect formation equations. 

Because of close packing in fee metals, the energy of interstitial formation in copper should be much higher than that of the vacancy Johnson and Wilson calculated a value of 63 kcal/mole. Using this value and 1.6 e.u. for the entropy of interstitial formation, K[ is found to be 4 x lO at 1000°K. For [A ] 1, this value also... 

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