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diff --git a/posic/publications/sic_prec.tex b/posic/publications/sic_prec.tex
index 3696eae7c31eff50361be9ceb8ae829fe1ecbc31..860fe77659247fd3516ef7ac6b74f525717da0a1 100644 (file)
--- a/posic/publications/sic_prec.tex
+++ b/posic/publications/sic_prec.tex
@@ -345,44 +345,28 @@ To support previous assumptions MD simulations, which are capable of modeling th
 
 In a previous comparative study\cite{zirkelbach10a} we have schown that the utilized empirical potential fails to describe some selected processes.
 Thus, limitations of the employed potential have been further investigated and taken into account in the present study.
-We focussed on two major shortcomings: the overestimated activation energy and the poor description of intrinsic and C point defects in Si.
+We focussed on two major shortcomings: the overestimated activation energy and the improper description of intrinsic and C point defects in Si.
+Overestimated forces between next neighbor atoms that are expected for short range potentials\cite{mattoni2007} have been confirmed to influence the C$_{\text{i}}$ diffusion.
+The migration barrier was estimated to be larger by a factor of 2.4 to 3.5 compared to highly accurate quantum-mechanical calculations\cite{zirkelbach10a}.
+Concerning point defects the drastically underestimated formation energy of C$_{\text{s}}$ and deficiency in the description of the Si$_{\text{i}}$ ground state necessitated further investigations on structures that are considered important for the problem under study.
+It turned out that the EA potential still favors a C$_{\text{i}}$ \hkl<1 0 0> DB over a C$_{\text{s}}$-Si$_{\text{i}}$ configuration, which, thus, does not constitute any limitation for the simulations aiming to resolve the present controversy of the proposed SiC precipitation models.
 
+MD simulations at temperatures used in IBS resulted in structures that were dominated by the C$_{\text{i}}$ \hkl<1 0 0> DB and its combinations if C is inserted into the total volume.
+Incoorporation into volmes $V_2$ and $V_3$ led to an amorphous SiC-like structure within the respective volume.
+To ensure correct diffusion behavior simulations at elevated temperatures have been performed.
+Although ...
 
+entropic contribution.
+as in \cite{zirkelbach10b}, next neighbored Cs and Sii did not recombine, but departed from each other.
 
 Sii stress compensation ...
+Thus, we prpopose (support) the follwing model ...
 
 Concluded that C sub is very probable ...
 Alignment lost, successive substitution more probable to end up with topotactic 3C-SiC.
 
-
 Both, low and high, acceleration not enough to either observe C agglomeration or amorphous to crystalline transition ...
 
-The first-principles results are in good agreement to previous work on this subject\cite{burnard93,leary97,dal_pino93,capaz94}.
-The C-Si \hkl<1 0 0> dumbbell interstitial is found to be the ground state configuration of a C defect in Si.
-The lowest migration path already proposed by Capaz et~al.\cite{capaz94} is reinforced by an additional improvement of the quantitative conformance of the barrier height calculated in this work (\unit[0.9]{eV}) with experimentally observed values (\unit[0.70]{eV} -- \unit[0.87]{eV})\cite{lindner06,song90,tipping87}.
-However, it turns out that the bond-centered configuration is not a saddle point configuration as proposed by Capaz et~al.\cite{capaz94} but constitutes a real local minimum if the electron spin is properly accounted for.
-A net magnetization of two electrons, which is already clear by simple molecular orbital theory considerations on the bonding of the sp hybridized C atom, is settled.
-By investigating the charge density isosurface it turns out that the two resulting spin up electrons are localized in a torus around the C atom.
-With an activation energy of \unit[0.9]{eV} the C$_{\text{i}}$ carbon interstitial can be expected to be highly mobile at prevailing temperatures in the process under investigation, i.e. IBS.
-
-We found that the description of the same processes fails if classical potential methods are used.
-Already the geometry of the most stable dumbbell configuration differs considerably from that obtained by first-principles calculations.
-The classical approach is unable to reproduce the correct character of bonding due to the deficiency of quantum-mechanical effects in the potential.
-%ref mod: language - energy / order 
-%Nevertheless, both methods predict the same type of interstitial as the ground state configuration, and also the order in energy of the remaining defects is reproduced fairly well.
-Nevertheless, both methods predict the same type of interstitial as the ground state configuration.
-Furthermore, the relative energies of the other defects are reproduced fairly well.
-From this, a description of defect structures by classical potentials looks promising.
-% ref mod: language - changed
-%However, focussing on the description of diffusion processes the situation is changing completely.
-However, focussing on the description of diffusion processes the situation has changed completely.
-Qualitative and quantitative differences exist.
-First of all, a different pathway is suggested as the lowest energy path, which again might be attributed to the absence of quantum-mechanical effects in the classical interaction model.
-Secondly, the activation energy is overestimated by a factor of 2.4 compared to the more accurate quantum-mechanical methods and experimental findings.
-This is attributed to the sharp cut-off of the short range potential.
-As already pointed out in a previous study\cite{mattoni2007} the short cut-off is responsible for overestimated and unphysical high forces of next neighbor atoms.
-The overestimated migration barrier, however, affects the diffusion behavior of the C interstitials.
-By this artifact the mobility of the C atoms is tremendously decreased resulting in an inaccurate description or even absence of the dumbbell agglomeration as proposed by the precipitation model.
 
 \section{Summary}