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2000-12-22. Activation energy for oxygen migration: ceria - calcia

GOAL

Evaluation of the activation energy for oxygen migration in $Ce_{(1-x)}Ca_xO_{2-x}$ as the difference between the maximum and minimum energy values along the energy profile for a migrating oxygen from $\left(\frac{1}{4},\frac{1}{4},\frac{1}{4}\right)$ to $\left(\frac{3}{4},\frac{1}{4},\frac{1}{4}\right)$ .

Results

$\begin{center}\vbox{\input{2000-12-22-01.pslatex} }\end{center}$

NOTE: as with the other dopants, apparent irregularities can be observed for some compositions

$\inittptctr \rcRoundingfalse \fpDecimalSign{.} \begin{threeparttable} \begin{tab... ...tant lowermost values for each composition. \end{tablenotes}\end{threeparttable}$

$\begin{center}\vbox{\input{2000-12-22-02.pslatex} }\end{center}$

Representative input file


opti conp defect
dump every 1 ca-fix-10-39.dump

maxcyc opt      200
maxcyc fit      200
title
Energy profile for oxygen migration
end

cell
   5.329267   5.329267   5.329267  90.000000  90.000000  90.000000

fractional    5
   Ce4  core  0.0000  0.0000  0.0000  -3.7000  0.9000  0.0000 
    Ca  core  0.0000  0.0000  0.0000   2.0000  0.1000  0.0000 
     O  core  0.2500  0.2500  0.2500   0.0770  0.9500  0.0000 
   Ce4  shel  0.0000  0.0000  0.0000   7.7000  0.9000  0.0000 
     O  shel  0.2500  0.2500  0.2500  -2.0770  0.9500  0.0000  
                                                     
space
225


size    10.38619969   21.81101935
centre          0.50   0.25   0.25
interstitial O  0.39   0.25   0.25  fix
vacancy         0.25   0.25   0.25
vacancy         0.75   0.25   0.25


buck
Ce4   shel O     shel  1986.8300     0.351070  20.400      0.000 15.000
Ca    core O     shel  1227.7        0.33720    0.000      0.0   15.0
O     shel O     shel 22764.300      0.149000  27.890      0.000 15.000
spring
Ce4    291.75000
O      27.290000