-Quantum-mechanical calculations reveal this configuration to be unstable, which is also reproduced by the Erhart/Albe potential.
-In both cases a relaxation towards the \hkl<1 0 0> dumbbell configuration is observed.
-In fact the stability of the hexagonal interstitial could not be reproduced in simulations performed in this work using the unmodifed Tersoff potential parameters.
-Unfortunately, apart from the modified parameters, no more conditions specifying the relaxation process are given in Tersoff's study on carbon point defects in silicon \cite{tersoff90}.
-
-The tetrahedral is the second most unfavorable interstitial configuration using classical potentials and keeping in mind the abrupt cutoff effect in the case of the Tersoff potential as discussed earlier.
-Again, quantum-mechanical results reveal this configuration unstable.
-The fact that the tetrahedral and hexagonal configurations are the two most unstable configurations in classical potential calculations and, thus, are less likely to arise in MD simulations acts in concert with the fact that these configurations are found to be unstable in the more accurate quantum-mechanical description.
-
-Just as for the Si self-interstitial a carbon \hkl<1 1 0> dumbbell configuration exists.
-For the Erhart/Albe potential the formation energy is situated in the same order as found by quantum-mechanical results.
-Similar structures arise in both types of simulations with the silicon and carbon atom sharing a silicon lattice site aligned along \hkl<1 1 0> where the carbon atom is localized slightly closer to the next nearest silicon atom located in the opposite direction to the site-sharing silicon atom even forming a bond to the next but one silicon atom in this direction.
-
-The bond-centered configuration is unstable for the Erhart/Albe potential.
-The system moves into the \hkl<1 1 0> interstitial configuration.
-This, like in the hexagonal case, is also true for the unmodified Tersoff potential and the given relaxation conditions.
+Quantum-mechanical calculations reveal this configuration to be unstable, which is also reproduced by the EA potential.
+In both cases a relaxation towards the \ci{} \hkl<1 0 0> DB configuration is observed.
+Opposed to results of the first-principles calculations, Tersoff finds this configuration to be stable \cite{tersoff90}.
+In fact, the stability of the hexagonal interstitial could not be reproduced in simulations performed in this work using the unmodifed Tersoff potential parameters.
+Unfortunately, apart from the modified parameters, no more conditions specifying the relaxation process are given in Tersoff's study on C point defects in Si.
+
+The tetrahedral is the second most unfavorable interstitial configuration using classical potentials if the abrupt cut-off effect of the Tersoff potential is taken into account.
+Again, quantum-mechanical results reveal this configuration to be unstable.
+The fact that the tetrahedral and hexagonal configurations are the two most unstable configurations in classical potential calculations and, thus, are less likely to arise in MD simulations, acts in concert with the fact that these configurations are found to be unstable in the more accurate quantum-mechanical description.
+
+Just as for \si{}, a \ci{} \hkl<1 1 0> DB configuration exists.
+It constitutes the second most favorable configuration, reproduced by both methods.
+Similar structures arise in both types of simulations.
+The Si and C atom share a regular Si lattice site aligned along the \hkl<1 1 0> direction.
+The C atom is slightly displaced towards the next nearest Si atom located in the opposite direction with respect to the site-sharing Si atom and even forms a bond with this atom.
+
+The \ci{} \hkl<1 1 0> DB structure is energetically followed by the BC configuration.
+However, even though EA based results yield the same difference in energy with respect to the \hkl<1 1 0> defect as DFT does, the BC configuration is found to be a unstable within the EA description.
+The BC configuration descends into the \ci{} \hkl<1 1 0> DB configuration.
+Due to the high formation energy of the BC defect resulting in a low probability of occurrence of this defect, the wrong description is not posing a serious limitation of the EA potential.
+Tersoff indeed predicts a metastable BC configuration.
+However, it is not in the correct order and lower in energy than the \ci{} \hkl<1 1 0> DB.