little more on increased temperatures, quality value defned

diff --git a/posic/thesis/md.tex b/posic/thesis/md.tex
index 2318a656d4accf8495570c45fa518d70a088fa39..a51304e8e9312cc4d205ba2a9cb52777772f501e 100644 (file)
--- a/posic/thesis/md.tex
+++ b/posic/thesis/md.tex
@@ -264,13 +264,21 @@ Due to the limitations of short range potentials and conventional MD as discusse
 The simulation sequence and other parameters aside system temperature remain unchanged as in section \ref{subsection:initial_sims}.
 Since there is no significant difference among the $V_2$ and $V_3$ simulations only the $V_1$ and $V_2$ simulations are carried on and refered to as low carbon and high carbon concentration simulations.
 Temperatures ranging from $450\,^{\circ}\mathrm{C}$ up to $2050\,^{\circ}\mathrm{C}$ are used.
-A quality value $Q$ is introduced, which is defined as
+A simple quality value $Q$ is introduced, which helps to estimate the progress of structural evolution.
+In bulk 3C-SiC every C atom has four next neighboured Si atoms and every Si atom four next neighboured C atoms.
+The quality could be determined by counting the amount of atoms which form bonds to four atoms of the other species.
+However, the aim of the simulation on hand is to reproduce the formation of a 3C-SiC precipitate embedded in c-Si.
+The amount of Si atoms and, thus, the amount of Si atoms remaining in the silicon diamond lattice is much higher than the amount of inserted C atoms.
+Thus, counting the atoms, which exhibit proper coordination is limited to the C atoms.
+The quality value is defined to be
 \begin{equation}
 Q = \frac{\text{Amount of C atoms with 4 next neighboured Si atoms}}
          {\text{Total amount of C atoms}} \text{ .}
 \label{eq:md:qdef}
 \end{equation}
-In 3C-SiC every C atom has four next neighboured Si atoms resulting in $Q=1$.
+By this, bulk 3C-SiC will still result in $Q=1$ and precipitates will also reach values close to one.
+However, since the quality value does not account for bond lengthes, bond angles, crystallinity or the stacking sequence high values of $Q$ not necessarily correspond to structures close to 3C-SiC.
+Structures that look promising due to high quality values need to be further investigated by other means.
 
 Figure ... shows the radial distribution of Si-C bonds and the corresponding quality paragraphs.