Defects in Ga, Cr, and In-doped CoO Page: 4 of 7
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The parameters of the shell model are fitted to reproduce the crystal
structure, elastic constants, low and high frequency dielectric constants of
appropriate oxides. The resulting parameters are presented in Table 1.
Table 1. The fitted -parameters for the shell model, where c and s stand for
core and shell, respectively.
species A (eV) B (A) C (eV/A6)
Co(c)-O(s) 778.02 0.3301 -
Co3+(c)-O(s) 1156.62 0.3087 -
Ga(c)-O(s) 1625.72 0.3019 -
Cr(c)-O(s) 1204.18 0.3165 -
In(s)-O(s) 1495.65 0.33272 4.3255
0(s)-O(s) 9547.96 0.21916 32.0
The calculated results for the point defects and defect clusters as
shown in Fig. 1 are shown in Tables 2 to 4. Table 2 shows that isolated point
defect energies, the singly charged pairs at the second nearest neighbor at
<110>, third nearest neighbor at <200>, and fourth nearest neighbor at <211>.
The energies for the singly charged pairs are measured relative to the
corresponding isolated point defects. Table 2 clearly shows that the Co(3+),
Cr(3+) and Ga(3+) ions prefer the third nearest neighbor position at <200>.
The binding energies are 0.80 eV for Co, 0.71 eV for Cr and 0.68 eV for Ga.
The corresponding experimental binding energies are 0.40 eV for Cr and
0.50 eV for Ga. The, agreement is fairly good. While In(3+) ion prefers the
second nearest neighbor distance at <110> with a binding energy of 0.77 eV,
but no experimental data are available. In ions are different from Ga , Cr
and Co ions. We have tried to calculate the energy without making the In
ion polarizable, but the result remained the same. It will be interesting to
see experiments done in locating the position of In ions in CoO relative to
the Co vacancies.
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Chen, S.P.; Yan, M.; Grimes, R.W. & Vyas, S. Defects in Ga, Cr, and In-doped CoO, article, July 1, 1995; New Mexico. (digital.library.unt.edu/ark:/67531/metadc794750/m1/4/: accessed September 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.