-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.
-
+\begin{figure}[h]
+\begin{center}
+\begin{minipage}{8cm}
+\includegraphics[width=8cm]{c_pd_vasp/bc_2333.eps}\\
+\hrule
+\vspace*{0.2cm}
+\includegraphics[width=8cm]{c_100_mig_vasp/im_spin_diff.eps}
+\end{minipage}
+\begin{minipage}{7cm}
+\includegraphics[width=7cm]{c_pd_vasp/bc_2333_ksl.ps}
+\end{minipage}
+\end{center}
+\caption[Structure, charge density isosurface and Kohn-Sham level diagram of the bond-centered interstitial configuration.]{Structure, charge density isosurface and Kohn-Sham level diagram of the bond-centered interstitial configuration. Gray, green and blue surfaces mark the charge density of spin up, spin down and the resulting spin up electrons in the charge density isosurface, in which the carbon atom is represented by a red sphere. In the energy level diagram red and green lines mark occupied and unoccupied states.}
+\label{img:defects:bc_conf}
+\end{figure}
+In the bond-centerd insterstitial configuration the interstitial atom is located inbetween two next neighboured silicon atoms forming linear bonds.
+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 an equivalent one \cite{capaz94}.
+This is in agreement with results of the Erhard/Albe potential simulations which reveal this configuration to be unstable relaxing into the \hkl<1 1 0> configuration.
+However, this fact could not be reproduced by spin polarized VASP calculations performed in this work.
+Present results suggest this configuration to be a real local minimum.
+In fact, an additional barrier has to be passed to reach this configuration starting from the \hkl<1 0 0> interstitital configuration, which is investigated in section \ref{subsection:100mig}.
+After slightly displacing the carbon atom along the \hkl<1 0 0> (equivalent to a displacement along \hkl<0 1 0>), \hkl<0 0 1> and \hkl<1 -1 0> direction the resulting structures relax back into the bond-centered configuration.
+As we will see in later migration simulations the same would happen to structures where the carbon atom is displaced along the migration direction, which approximately is the \hkl<1 1 0> direction.
+These relaxations indicate that the bond-cenetered configuration is a real local minimum instead of an assumed saddle point configuration.
+Figure \ref{img:defects:bc_conf} shows the structure, the charge density isosurface and the Kohn-Sham levels of the bond-centered configuration.
+The linear bonds of the carbon atom to the two silicon atoms indicate the $sp$ hybridization of the carbon atom.
+Two electrons participate to the linear $\sigma$ bonds with the silicon neighbours.
+The other two electrons constitute the $2p^2$ orbitals resulting in a net magnetization.
+This is supported by the charge density isosurface and the Kohn-Sham levels in figure \ref{img:defects:bc_conf}.
+The blue torus, reinforcing the assumption of the p orbital, illustrates the resulting spin up electron density.
+In addition, the energy level diagram shows a net amount of two spin up electrons.