Defects formation enthalpy

The activation energy for self-diffusivity of the Ag cations by the interstitialcy mechanisms is the sum of one-half the Frenkel defect formation enthalpy and the activation enthalpy for migration,... 

Fig. 1.13. Top Variation of defect formation enthalpies with Fermi level under zinc- (left) and oxygen-rich (right) conditions as obtained from GGA+U calculations. The gray shaded area indicates the difference between the calculated and the experimental band gap. The numbers in the plot indicate the defect charge state parallel lines imply equal charge states Bottom Transition levels in the band gap calculated within GGA (a), GGA+U (b) and using an extrapolation formula described in [115]. The dark gray shaded areas indicate error bars. Copyright (2006) by the American Physical Society...

In recent years, there has been considerable effort to derive defect formation enthalpies of intrinsic defects in ZnO [108-110,113-117]. An example is shown in Fig. 1.13 [115]. Horizontal curves belong to neutral defects, curves with positive or negative slopes to charged donors or acceptors, respectively. The donor with the lowest formation enthalpy is the oxygen vacancy Vo, the acceptor with the lowest formation enthalpy the zinc vacancy Vzn-... 

This corresponds to a Frenkel type defect behavior. Negative defect formation enthalpies corresponds to unstable crystals (spontaneous defect formation) and indicate the limit for physically reasonable Fermi level positions. 

Schottky defects, formation enthalpy 77 lithium chloride, LiCl... 

If an oxide has a sufficiently large bandgap (small X,), the stoichiometric oxide MO (in the center of the electrolytic domain) is an ion conductor. Assume that K /Ki =10 and that the Schottky defect formation enthalpy is 2 eV. What is the bandgap energy of the... 

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