+Results of combinations of \ci{} and \cs{} revealed two additional metastable structures different to these obtained by a naive relaxation.
+Small displacements result in a structure of a \hkl<1 1 0> C-C DB and in a structure of a twofold coordinated Si atom located in between two substitutional C atoms residing on regular Si lattice sites.
+Both structures are lower in energy compared to the respetive counterparts.
+These results, for the most part, compare well with results gained in previous studies \cite{leary97,capaz98,liu02} and show an astonishingly good agreement with experiment \cite{song90_2}.
+Again, spin polarized calculations are revealed necessary.
+A net magnetization of two electrons is observed for the \hkl<1 1 0> C-C DB configuration, which constitutes the ground state.
+A repulsive interaction is observed for C$_{\text{s}}$ at lattice sites along \hkl[1 1 0] due to tensile strain originating from both, the C$_{\text{i}}$ DB and the C$_{\text{s}}$ atom.
+All other investigated configurations show attractive interactions, which suggest an energetically favorable agglomeration of C$_{\text{i}}$ and C$_{\text{s}}$ except for separations along one of the \hkl<1 1 0> directions.
+Although the most favorable configuration exhibits a C-C bond, migration paths show large barriers exceeding \unit[2.2]{eV} for transitions into the ground state.
+As before, structures other than the ground-state configuration are assumed to arise more likely.
+Thus, agglomeration of C defects in contrast to C clustering is again reinforced by these findings.
+
+C$_{\text{i}}$ and vacancies are found to efficiently react with each other exhibiting activation energies as low as \unit[0.1]{eV} and \unit[0.6]{eV} resulting in stable C$_{\text{s}}$ configurations.
+In addition, a highly attractive interaction exhibiting a large capture radius, effective independent of the orientation and the direction of separation of the defects, is observed.
+Accordingly, the formation of C$_{\text{s}}$ is very likely to occur.
+Comparatively high energies necessary for the reverse process reveal this configuration to be extremely stable.
+Thus, C interstitials and vacancies located close together are assumed to end up in a configuration of \cs{}.
+
+Investigating configurations of C$_{\text{s}}$ and Si$_{\text{i}}$, formation energies higher than that of the C$_{\text{i}}$ \hkl<1 0 0> DB were obtained keeping up previously derived assumptions concerning the ground state of C$_{\text{i}}$ in otherwise perfect Si.
+However, a small capture radius is identified for the respective interaction that might prevent the recombination of defects exceeding a separation of \unit[0.6]{nm} into the ground-state configuration.
+In addition, a rather small activation energy of \unit[0.77]{eV} allows for the formation of a C$_{\text{s}}$-Si$_{\text{i}}$ pair originating from the C$_{\text{i}}$ \hkl<1 0 0> DB structure by thermally activated processes.
+Low diffusion barriers of \si{} enable further separation of the defect pair.
+Thus, elevated temperatures might lead to configurations of C$_{\text{s}}$ and a remaining Si atom in the near interstitial lattice, which is likewise supported by the result of the MD run.
+
+% maybe preliminary conclusions here ...
+
+Classical potential MD calculations targeting the direct simulation of SiC precipitation in Si are adopted.
+Therefore, the necessary amount of C is gradually incorporated into a large c-Si host.
+Simulations at temperatures used in IBS result in structures dominated by the C$_{\text{i}}$ \hkl<1 0 0> DB and its combinations if C is inserted into the total volume.
+Incorporation into volumes $V_2$ and $V_3$, which correspond to the volume of the expected precipitate and the volume containing the necessary amount of Si, lead to an amorphous SiC-like structure within the respective volume.
+Both results are not expected with respect to the outcome of the IBS experiments.
+In the first case, i.e. the low C concentration simulations, \ci{} \hkl<1 0 0> DBs are indeed formed.
+However, sufficient defect agglomeration is not observed.
+In the second case, i.e. the high C concentration simulations, crystallization of the amorphous structure, which is not expected at prevailing temperatures, is likewise not observed.
+
+Limitations of the MD technique in addition to overestimated bond strengths due to the short range potential are identified to be responsible.
+The approach of using increased temperatures during C insertion is followed to work around this problem termed {\em potential enhanced slow phase space propagation}.
+Higher temperatures are justified for severeal reasons.
+Elevated temperatures are expected to compensate the overestimated diffusion barriers and accelerate strcutural evolution.
+In addition, formation of SiC is also observed at higher implantation temperatures \cite{nejim95,lindner01} and temperatures in the implantation region is definetly higher than the temperature determined experimentally at the surface of the sample.
+Furthermore, the present study focuses on structural transitions in a system far from equilibrium.
+
+No significant change is observed for high C concentrations at increased temperatures.
+The amorphous phase is maintained.
+The huge amount of damage hampers identification of investigated structures, which in many cases lost the alignment to the c-Si host.
+Obviously, inccorporation of a high quantity of C into a small volume within a short period of time creates damage, which decelerates structural evolution.
+For the low C concentrations, time scales are still too low to observe C agglomeration.
+However, a phase transition of the C$_{\text{i}}$-dominated into a clearly C$_{\text{s}}$-dominated structure is observed.
+The amount of \cs{} increases with increasing temperature.
+Diamond and graphite like bonds as well as the artificial bonds due to the cut-off are reduced.
+Loose structures of stretched SiC, which are adjusted to the Si lattice with respect to the lattice constant and alignment, are identified.
+\si{} is often found in the direct surrounding.
+Entropic contributions are assumed to be responsible for these structures at elevated temperatures that deviate from the ground state at 0 K.
+Indeed, utilizing increased temperatures is assumed to constitute a necessary condition to simulate IBS of 3C-SiC in c-Si.
+
+% conclusions 2nd part
+\paragraph{Conclusions}
+concerning the SiC conversion mechanism are derived from results of both, first-principles and classical potential calculations.
+Although classical potential MD calculations fail to directly simulate the precipitation of SiC, obtained results, on the one hand, reinforce previous findings of the first-principles investigations and, on the other hand, allow further conclusions on the SiC precipitation in Si.
+
+Initially, quantum-mechanical investigations suggest agglomeration of \ci{} defects that form energetically favorable configurations by an effective stress compensation.
+Low barriers of migration are found except for transitions into the ground-state configuration, which is composed of a strong C-C bond.
+Thus, agglomeration of \ci{} in the absence of C clsutering is expected.
+These initial results suggest a conversion mechansim based on the agglomeration of \ci{} defects followed by a sudden precipitation once a critical size is reached.
+However, subsequent investigations of structures that are particularly conceivable under conditions prevalant in IBS and at elevated temperatures show \cs{} to occur in all probability.
+The transition from the ground state of a single C atom incorporated into otherwise perfect c-Si, i.e. the \ci{} \hkl<1 0 0> DB, into a configuration of \cs{} next to a \si{} atom exhibits an activation energy lower than the one for the diffusion of the highly mobile \ci{} defect.
+Considering additionally the likewise lower diffusion barrier of \si{}, configurations of separated \cs{} and \si{} will occur in all probability.
+This is reinforced by the {\em ab initio} MD run at non-zero temperature, which shows structures of separating instead of recombining \cs{} and \si{} defetcs.
+This suggests increased participation of \cs{} already in the initial stages of the implantation process.
+The highly mobile \si{} is assumed to constitute a vehicle for the rearrangement of other \cs{} atoms onto proper lattice sites, i.e. lattice sites of one of the the two fcc lattices composing the diamond structure.
+This way, stretched SiC strcutures, which are coherently aligned to the c-Si host, are formed by agglomeration of \cs.
+Precipitation into an incoherent and partially strain-compensated SiC nucleus occurs once the increasing strain energy surpasses the interfacial energy of the incoherent 3C-SiC precipitate and the c-Si substrate.
+As already assumed by Nejim~et~al.~\cite{nejim95}, \si{} serves as supply for subsequently implanted C atoms to form further SiC in the resulting free space due to the accompanied volume reduction.
+
+Several conclusions based on results obtained by classical potential MD simulations are drawn.
+First of all, increased temperatures are considered a necessary condition to simulate the IBS of epitaxially aligned 3C-SiC in Si, which constitutes a process far from thermodynamic equilibrium.
+The strong deviation from equilibrium by elevated temperatures enables the formation of \cs{}-\si{} structures as observed in the quantum-mechanical calculations.
+In contrast, structures of \ci{} \hkl<1 0 0> DBs, which constitute the thermodynamic ground state, appear at low temperatures.
+%
+Secondly, in configurations of stretched SiC composed by \cs, the accompanied \si{} defect may be assigned further functionality.
+Next to that as a vehicle that is able to rearrange \cs{} and a building block for the surrounding Si host or further SiC, the analyzed configurations suggest \si{} to be required for stress compensation.
+As evidently observed in these structures, \si{} reduces tensile strain by capturing a position near one of the C atoms within a configuration of two C atoms that basically reside on Si lattice sites.
+Furthermore, \si{} might compensate strain in the interface region of an incoherent, nucleated SiC precipitate and the c-Si matrix.
+This could be achieved by \ci{} \hkl<1 0 0> DBs in the Si region slightly contracting the Si atoms next to the C atom to better match the spacing of Si atoms present in 3C-SiC.
+Indeed, combinations of \cs{} and \ci{} \hkl<1 0 0> DBs are observed.
+%
+Further conclusions are derived from results of the high C concentration simulations, in which a large amount of C atoms is incorporated into a small volume within a short period of time, which results in essentially no time for the system to rearrange.
+Due to this, the formation of strong C-C bonds and the production of a vast amount of damage is observed, which finally results in the formation of an amorphous phase.
+The strong bonds and damage obviously decelerate structural evolution.
+The short time, which is not sufficient for structural evolution, can be mapped to a system of low temperature, which lacks the kinetic energy required for the restructuring process.
+
+
+HIER WEITER ...