Conclusions on the precipitation based on the DFT results are drawn.
In the second part, classical potential MD simulations are performed, which try to directly reproduce the precipitation.
Next to the shortcomings of the potential, quirks inherent to MD are discussed and a workaround is proposed.
-Although direct formation of SiC fails to appear, the results suggest a mechanism of precipitation, which is consistent with previous quantum-mechanical conclusions as well as experimental findings.
+Although direct formation of SiC fails to appear, the obtained results indicate a mechanism of precipitation, which is consistent with previous quantum-mechanical conclusions as well as experimental findings.
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+Quantum-mechanical results of intrinsic point defects in Si are in good agreement to previous theoretical work on this subject \cite{leung99,al-mushadani03}.
+The \si{} \hkl<1 1 0> DB defect is reproduced as the ground-state configuration followed by the hexagonal and tetrahedral defect.
+Spin polarized calculations are required for the \si{} \hkl<1 0 0> DB and vacancy whereas no other of the investigated intrinsic defects is affected.
+For the \si{} \hkl<1 0 0> DB, the net spin up density is localized in two caps at each of the two DB atoms perpendicularly aligned to the bonds to the other two Si atoms.
+For the vacancy, the net spin up electron density is localized in caps at the four surrounding Si atoms directed towards the vacant site.
+Results obtained by calculations utilizing the classical EA potential yield formation energies, which are of the same order of magnitude.
+However, EA predicts the tetrahedral configuration to be most stable.
+The particular problem is due to the cut-off and the fact that the second neighbors are only slightly more distant than the first neighbors within the tetrahedral configuration.
+Furthermore, the hexagonal defect structure is not stable opposed to results of the authors of the potential \cite{albe_sic_pot}.
+The obtained structure after relaxation, which is similar to the tetrahedral configuration, has a formation energy equal to the one given by the authors for the hexagonal one.
+Obviously, the authors did not check the structure after relaxation still assuming a hexagonal configuration.
+The actual structure equals the tetrahedral configuration, which is slightly displaced along the three coordinate axes.
+Variations exist with displacements along two or a single \hkl<1 0 0> direction indicating a potential artifact.
+However, finite temperature simulations are not affected by this artifact due to a low activation energy necessary for a transition into the energetically more favorable tetrahedral configuration.
+Next to the known problem of the underestimated formation energy of the tetrahedral configuration \cite{tersoff90}, the energetic sequence of the defect structures is well reproduced by the EA calculations.
+Migration barriers of \si{} investigated by quantum-mechanical calculations are found to be of the same order of magnitude than values derived in other ab initio studies \cite{bloechl93,sahli05}.
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+HIER WEITER
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+Defects of C in c-Si are well described by both methods.
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-Obtained results
projects / lectures / latex.git / blobdiff