Next: 2000-03-03: correction for partial Up: simulation in ceria-zirconia mixed Previous: 2000-02-23: changing the initial

2000-02-25: trying a different potential set Bush et al. (1994)

GOAL

We extend the calculation in 2000-02-21 with the potential of Bush et al. (1994), still in the attempt of reproducing experimental results in Sakai et al. (1999).

The initial orientation of the group was along the crystallographic direction, i.e. along the face diagonal of the cube of oxygen atoms inside the unit cell. Moreover, relaxation of the defect was done without simmetry (i.e. the keyword nodsymmetry was used).

Results

$\fbox { \begin{minipage}{0.6\linewidth} \bf Mon Mar 6 18:28:52 2000\\ Mean field correction NOT applied here. See 2000-03-03 \end{minipage}}%\fbox$

$E_{OH_O^\cdot }$ evaluation

Details for $E_{H_2O}$ evaluation can be found in 2000-02-02 (3).

$\begin{center} \begin{threeparttable} \begin{tabular}{lD{.}{.}{6}D{.}{.}{6}D{.}{... ...$} &5.570822& 9.99367280 & 774 \\ \end{tabular}\end{threeparttable}\end{center}$

Note: this potential set gives relaxed lattice parameters considerably longer than experimental values.

$\begin{center} \begin{threeparttable} \begin{tabular}{lD{.}{.}{10}D{.}{.}{10}D{.... ....52196488 & 13.57446488 & 2.12 \\ \end{tabular}\end{threeparttable}\end{center}$

$E_{V_O^{\cdot \cdot }}$ evaluation

$\begin{threeparttable} \begin{tabular}{lD{.}{.}{6}D{.}{.}{6}D{.}{.}{0}D{.}{.}{6}... ...0822 & 9.99367280 & 772 & 9.69805970 &1.29 \\ \end{tabular}\end{threeparttable}$

$E_{H_2O}$ evaluation

$\begin{center} \begin{threeparttable} \begin{tabular}{lD{.}{.}{10}D{.}{.}{10}D{.... ...6488 & 9.69805970 & 5.68087006 \\ \end{tabular}\end{threeparttable}\end{center}$

$\begin{center}\vbox{\input{2000-02-25-01.pslatex} }\end{center}$

Apart from the unphysical lattice parameters, the trend is still opposite to the experimental one.

Geometry of the optimized defect

The following table shows the angle $\theta$ between the $\xy* {O};p+/r2em/*{H}**\dir{-}?>*\dir{>}\endxy$ vector and the direction, and the $\xy*{O};p+/r2em/*{H}**\dir{-}\endxy$ bond length:

$\begin{center} \begin{threeparttable} \begin{tabular}{lllll} \multicolumn{1}{c}{... ...2 & 2.211025,2.211040,2.211008 \\ \end{tabular}\end{threeparttable}\end{center}$

$\begin{center} \begin{threeparttable} \begin{tabular}{lll} \multicolumn{1}{c}{Ox... ...9}$} & 0.00148085 & 0.96729668 \\ \end{tabular}\end{threeparttable}\end{center}$

Representative input files

$E_{OH_O^{\cdot }}$


opti conp defect regi_before nodsymmetry
#conp defect single
dump every 1 nd-OH.dump
maxcyc  200
cutb 3.0 # what does this mean? Ronny uses it.
title
Neodimium solid solution
N.Sakai et al. Solid State Ionics 125(1999)325-331
end
cell
   5.490000 5.490000 5.490000  90.000000  90.000000  90.000000

size 10.06309257    20.0
centre      0.25   0.25   0.25
impurity     O2 core   0.25   0.25   0.25
interstitial H2 core   0.37354608 0.37354608 0.25000000
fractional   
############
# Cores
############
Ce4  core  0.000000   0.000000   0.000000  -3.700000 0.8
Nd   core  0.000000   0.000000   0.000000   1.678    0.2
O1   core  0.250000   0.250000   0.250000   0.51300  0.95
############
# Shells
############
Ce4  shel  0.000000   0.000000   0.000000   7.700000 0.8
Nd   shel  0.000000   0.000000   0.000000   1.322    0.2
O1   shel  0.250000   0.250000   0.250000  -2.51300  0.95
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
Ce3 shel O1 shel    1731.61808  0.36372    14.43256  0.0 15.000
Nd  shel O1 shel   13084.217    0.2550      0.00     0.0 15.000
O1  shel O1 shel      25.410000 0.69370    32.32000  0.0 15.000
O2  core O1 shel      25.410000 0.69370    32.32000  0.0 15.000
H2  core O1 shel     311.970    0.35        0.0      0.0 15.000
Ce4 shel O2 core    1986.830000 0.351070   20.40000  0.0 15.000
Nd  shel O2 core   13084.217    0.2550      0.00     0.0 15.000
morse
H2  core O2 core       7.05250  2.19860     0.9485   1.0 0.0 2.0
#########################
# Spring parameters
#########################
spring 
Ce4    291.75
Ce3    291.75
Nd     302.35
O1      20.53

$E_{V_O^{\cdot \cdot }}$


opti conp defect regi_before nodsymmetry
#conp defect single
dump every 1 nd-Ovaca.dump
maxcyc  200
cutb 3.0 # what does this mean? Ronny uses it.
title
Neodimium solid solution
N.Sakai et al. Solid State Ionics 125(1999)325-331
end
cell
   5.490000 5.490000 5.490000  90.000000  90.000000  90.000000

size 10.06309257    20.0
centre      0.25   0.25   0.25
#impurity     O2 core   0.25   0.25   0.25
#interstitial H2 core   0.37354608 0.37354608 0.25000000
vacancy       0.25      0.25       0.25
fractional   
############
# Cores
############
Ce4  core  0.000000   0.000000   0.000000  -3.700000 0.8
Nd   core  0.000000   0.000000   0.000000   1.678    0.2
O1   core  0.250000   0.250000   0.250000   0.51300  0.95
############
# Shells
############
Ce4  shel  0.000000   0.000000   0.000000   7.700000 0.8
Nd   shel  0.000000   0.000000   0.000000   1.322    0.2
O1   shel  0.250000   0.250000   0.250000  -2.51300  0.95
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
Ce3 shel O1 shel    1731.61808  0.36372    14.43256  0.0 15.000
Nd  shel O1 shel   13084.217    0.2550      0.00     0.0 15.000
O1  shel O1 shel      25.410000 0.69370    32.32000  0.0 15.000
O2  core O1 shel      25.410000 0.69370    32.32000  0.0 15.000
H2  core O1 shel     311.970    0.35        0.0      0.0 15.000
Ce4 shel O2 core    1986.830000 0.351070   20.40000  0.0 15.000
Nd  shel O2 core   13084.217    0.2550      0.00     0.0 15.000
morse
H2  core O2 core       7.05250  2.19860     0.9485   1.0 0.0 2.0
#########################
# Spring parameters
#########################
spring 
Ce4    291.75
Ce3    291.75
Nd     302.35
O1      20.53

Next: 2000-03-03: correction for partial Up: simulation in ceria-zirconia mixed Previous: 2000-02-23: changing the initial