2000-01-20: influence of region 1 radius on $E_{OH_{O}^\cdot }$

GOAL

Explorative calculations on the $Ce_{0.5}Zr_{0.5}O_2$ system: input file was constructed after the one sent by Ronny. Energy of the $OH_{O}^\cdot$ defect at increasing region 1 radius.

Results

Representative input file:

opti conp defect regi_before
#conp defect single
dump every 1 gulp-09.dump
maxcyc  200
cutb 3.0 # what does this mean? Ronny uses it.
title
adjusting region 1 radius
end
cell
   5.274196 5.274196 5.274196  90.000000  90.000000  90.000000

size        09.0     20.00
centre                 0.251  0.249  0.25
impurity     O2 core   0.25   0.25   0.25
interstitial H2 core   0.44   0.25   0.25
fractional   
############
# Cores
############
Ce4  core  0.000000   0.000000   0.000000  -3.700000 0.50
Zr   core  0.000000   0.000000   0.000000   2.65     0.50
O1   core  0.250000   0.250000   0.250000   0.07700  1.00  
############
# Shells
############
Ce4  shel  0.000000   0.000000   0.000000   7.700000 0.50
Zr   shel  0.000000   0.000000   0.000000   1.35     0.50
O1   shel  0.250000   0.250000   0.250000  -2.07700  1.00 
space
225

#########################
# Shell-core charges
#########################
species   
Ce3   shel    7.700000
Ce3   core   -4.700000   
O2    core   -1.4263
H2    core    0.4263         
#########################
# Short range potentials
#########################
buck 
Ce4 shel O1 shel    1986.830000 0.351070   20.40000  0.0 15.000
buck                                                    
Ce3 shel O1 shel    1731.61808  0.36372    14.43256  0.0 15.000
buck                                                    
Zr  shel O1 shel     985.869000 0.376000    0.00000  0.0 15.000
buck                                                    
O1  shel O1 shel   22764.300000 0.149000   27.89000  0.0 15.000
buck                                                    
O2  core O1 shel   22764.300000 0.149000   27.89000  0.0 15.000
buck                                                    
H2  core O1 shel     311.970    0.35        0.0      0.0 15.000
morse
H2  core O2 core       7.05250  2.19860     0.9485   1.0 0.0 2.0
buck 
Ce4 shel O2 core    1986.830000 0.351070   20.40000  0.0 15.000
buck                                                    
Zr  shel O2 core     985.869000 0.376000    0.00000  0.0 15.000
#########################
# Spring parameters
#########################
spring 
Ce4    291.750000
spring 
Ce3    291.750000
spring 
Zr     169.617000
spring 
O1     27.29

The following table lists the formation energies for the $OH_{O}^\cdot$ defect (no $D$ addition) at increasing region 1 radius (region 2a radius is fixed at $20.0\;\mbox{\it\AA}$):

Taking the value of $(11.11243062+7.05250)\;eV$ for $E_{OH_O^\cdot }$, $E_{V_O^{\cdot\cdot}}=16.23707892\;eV$ from previous work Balducci et al. (1997) and $E_{PT}=-11.77\;eV$ from Glockner et al. (1999), the energy change for water incorporation:

$$\begin{eqnarray*} H_2O_{(g)}+V_O^{\cdot\cdot}+O_O^\times&=&2OH_O^\cdot \end{eqnarray*}$$

is calculated to be: $E_{H_2O}=E_{PT}+2E_{OH_O^\cdot}-E_{V_O^{\cdot\cdot}}=8.32278232\;eV$, which is extremely higher than the values reported in Glockner et al. (1999).