bc conf

diff --git a/posic/thesis/defects.tex b/posic/thesis/defects.tex
index c286426133078b5fe4127486a2a5b76b83958211..1e37879394067fdc45041e1059f03d2f45b3e90e 100644 (file)
--- a/posic/thesis/defects.tex
+++ b/posic/thesis/defects.tex
@@ -345,7 +345,7 @@ Displacements\\
 \hline
 \hline
  & & & & \multicolumn{3}{c}{Atom 2} & \multicolumn{3}{c}{Atom 3} \\
-and bond angles  & $a$ & $b$ & $|a|+|b|$ & $\Delta x$ & $\Delta y$ & $\Delta z$ & $\Delta x$ & $\Delta y$ & $\Delta z$ \\
+ & $a$ & $b$ & $|a|+|b|$ & $\Delta x$ & $\Delta y$ & $\Delta z$ & $\Delta x$ & $\Delta y$ & $\Delta z$ \\
 \hline
 Erhard/Albe & 0.084 & -0.091 & 0.175 & -0.015 & -0.015 & -0.031 & -0.014 & 0.014 & 0.020 \\
 VASP & 0.109 & -0.065 & 0.174 & -0.011 & -0.011 & -0.024 & -0.014 & 0.014 & 0.025 \\
@@ -400,6 +400,14 @@ VASP & 130.7 & 114.4 & 146.0 & 107.0 \\
 \caption{Comparison of the visualized \hkl<1 0 0> dumbbel structures obtained by Erhard/Albe potential and VASP calculations.}
 \label{fig:defects:100db_vis_cmp}
 \end{figure}
+\begin{figure}[h]
+\begin{center}
+\includegraphics[height=10cm]{c_pd_vasp/eden.eps}
+\includegraphics[height=12cm]{c_pd_vasp/100_2333_ksl.ps}
+\end{center}
+\caption[Charge density isosurface and Kohn-Sham levels of the C \hkl<1 0 0> dumbbell structure obtained by VASP calculations.]{Charge density isosurface and Kohn-Sham levels of the C \hkl<1 0 0> dumbbell structure obtained by VASP calculations. Yellow and grey spheres correspond to silicon and carbon atoms. The blue surface is the charge density isosurface. In the energy level diagram red and green lines and dots mark occupied and unoccupied states.}
+\label{img:defects:charge_den_and_ksl}
+\end{figure}
 The silicon atom numbered '1' and the C atom compose the dumbbell structure.
 They share the lattice site which is indicated by the dashed red circle and which they are displaced from by length $a$ and $b$ respectively.
 The atoms no longer have four tetrahedral bonds to the silicon atoms located on the alternating opposite edges of the cube.
@@ -408,15 +416,30 @@ One bond is formed to the other dumbbell atom.
 The other two bonds are bonds to the two silicon edge atoms located in the opposite direction of the dumbbell atom.
 The distance of the two dumbbell atoms is almost the same for both types of calculations.
 However, in the case of the VASP calculation, the dumbbell structure is pushed upwards compared to the Erhard/Albe results.
-Thus, the angles of bonds of the silicon dumbbell atom are clos to $120^{\circ}$ signifying the predominance of $sp^2$ hybridization.
-On the other hand, the carbon atom forms an almost colinear bond with the two silicon edge atoms implying the predominance of $p$ and $sp$ bonding.
-This is   in figure \ref{fig:defects:100db_vis_cmp} as well as by the ...
+This is easily identified by comparing the values for $a$ and $b$ and the two structures in figure \ref{fig:defects:100db_vis_cmp}.
+Thus, the angles of bonds of the silicon dumbbell atom ($\theta_1$ and $\theta_2$) are closer to $120^{\circ}$ signifying the predominance of $sp^2$ hybridization.
+On the other hand, the carbon atom forms an almost collinear bond ($\theta_3$) with the two silicon edge atoms implying the predominance of $p$ and $sp$ bonding.
+This is supported by the image of the charge density isosurface in figure \ref{img:defects:charge_den_and_ksl}.
+In the same figure the Kohn-Sham levels are shown.
+There is no magnetization density.
+An acceptor level arises resulting in a band gap of 0.35 eV compared to 0.75 eV as obtained for plain silicon.
 
 \subsection{Bond-centered interstitial configuration}
 \label{subsection:bc}
 
+In the bond-centerd insterstitial configuration the interstitial atom is located inbetween two next neighboured silicon atoms.
+In former studies this configuration is found to be an intermediate saddle point configuration determining the migration barrier of one possibe migration path of a \hkl<1 0 0> dumbbel configuration into another one \cite{capaz94}.
+Hier ist es aber ein echtes Minimum.
+Eine 'weitere' Barriere muss ueberschritten werden um dahin zu kommen.
+Genaueres in section \ref{subsection:100mig}.
+Die Konfiguration besitzt ein magnetisches Moment.
+Bild der spin-ladungen.
+
+
 \section[Migration of the carbon \hkl<1 0 0> interstitial]{\boldmath Migration of the carbon \hkl<1 0 0> interstitial}
 \label{subsection:100mig}
 
+In the following the problem of interstitial carbon migration in silicon is considered.
+
 \section{Combination of point defects}