From: hackbard Date: Mon, 23 Aug 2010 17:33:49 +0000 (+0200) Subject: values of done calcs X-Git-Url: https://hackdaworld.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a546692efb3cc36fdc1a53b236fe191828972405;p=lectures%2Flatex.git values of done calcs --- diff --git a/posic/publications/defect_combos.tex b/posic/publications/defect_combos.tex index 33edd58..d6a18da 100644 --- a/posic/publications/defect_combos.tex +++ b/posic/publications/defect_combos.tex @@ -242,12 +242,12 @@ Configurations, which exhibit both, a low binding energy as well as afferent tra On the other hand, if elevated temperatures enable migrations with huge activation energies, comparably small differences in configurational energy can be neglected resulting in an almost equal occupation of such configurations. In both cases the configuration yielding a binding energy of \unit[-2.25]{eV} is promising. First of all, it constitutes the second most energetically favorable structure. -Secondly, a migration path with a barrier as low as \unit[?.?]{eV} exists starting from a configuration of largely separated defects exhibiting a low binding energy (\unit[-1.88]{eV}). +Secondly, a migration path with a barrier as low as \unit[0.47]{eV} exists starting from a configuration of largely separated defects exhibiting a low binding energy (\unit[-1.88]{eV}). The migration barrier and correpsonding structures are shown in Fig.~\ref{fig:188-225}. % 188 - 225 transition in progress \begin{figure} \includegraphics[width=\columnwidth]{188-225.ps} -\caption{Migration barrier and structures of the transition of a C$_{\text{i}}$ \hkl[0 -1 0] DB at position 5 (left) into a C$_{\text{i}}$ \hkl[1 0 0] DB at position 1 (right). An activation energy of \unit[?.?]{eV} is observed.} +\caption{Migration barrier and structures of the transition of a C$_{\text{i}}$ \hkl[0 -1 0] DB at position 5 (left) into a C$_{\text{i}}$ \hkl[1 0 0] DB at position 1 (right). An activation energy of \unit[0.47]{eV} is observed.} \label{fig:188-225} \end{figure} Finally, this type of defect pair is represented four times (two times more often than the ground state configuration) within the systematically investigated configuration space. @@ -307,7 +307,7 @@ Fig.~\ref{fig:093-095} and \ref{fig:026-128} show structures A, B and a, b toget %./visualize_contcar -w 640 -h 480 -d results/c_00-1_c3_csub_B -nll -0.20 -0.4 -0.1 -fur 0.9 0.6 0.9 -c 0.5 -1.5 0.375 -L 0.5 0 0.3 -r 0.6 -A -1 2.465 \begin{figure} \includegraphics[width=\columnwidth]{093-095.ps} -\caption{Migration barrier and structures of the transition of the initial C$_{\text{i}}$ \hkl[0 0 -1] DB and C$_{\text{s}}$ at position 3 (left) into a configuration of a twofold coordinated Si$_{\text{i}}$ located inbetween two C$_{\text{s}}$ atoms occupying the lattice sites of the initial DB and position 3 (right). An activation energy of \unit[0.?]{eV} is observed.} +\caption{Migration barrier and structures of the transition of the initial C$_{\text{i}}$ \hkl[0 0 -1] DB and C$_{\text{s}}$ at position 3 (left) into a configuration of a twofold coordinated Si$_{\text{i}}$ located inbetween two C$_{\text{s}}$ atoms occupying the lattice sites of the initial DB and position 3 (right). An activation energy of \unit[0.44]{eV} is observed.} \label{fig:093-095} \end{figure} Configuration A consists of a C$_{\text{i}}$ \hkl[0 0 -1] DB with threefold coordinated Si and C DB atoms slightly disturbed by the C$_{\text{s}}$ at position 3, facing the Si DB atom as a next neighbor. @@ -320,6 +320,8 @@ Present results show a difference in energy of states A and B, which exactly mat % % AB transition % ... +The migration barrier was identified to be \unit[0.44]{eV}, almost three times higher than the experimentally obtained value of \unit[0.16]{eV}\cite{song90_2}. +This might be due to % a b \begin{figure} @@ -339,9 +341,9 @@ A net magnetization of two spin up electrons, which are euqally localized as in Configurations a, A and B are not affected by spin polarization and show zero magnetization. Mattoni et~al.\cite{mattoni2002}, in contrast, find configuration b less favorable than configuration A by \unit[0.2]{eV}. Next to differences in the XC-functional and plane-wave energy cut-off this discrepancy might be attributed to the missing accounting for spin polarization in their calculations, which -- as has been shown for the C$_{\text{i}}$ BC configuration -- results in an increase of configurational energy. -Indeed, investigating the migration path from configurations a to b and, in doing so, reusing the wave functions of the previous migration step the final structure, i.e. configuration b, was obtained with zero magnetization and an increase in configurational energy \unit[0.2]{eV}. -Obviously a different energy minimum of the electronic system is obatined in that case showing a hysterisis behavior. -However, since the total energy is lower for the magnetic result it is believed to constitute the real, i.e. global, minimum of the electronic minimization. +Indeed, investigating the migration path from configurations a to b and, in doing so, reusing the wave functions of the previous migration step the final structure, i.e. configuration b, was obtained with zero magnetization and an increase in configurational energy by \unit[0.2]{eV}. +Obviously a different energy minimum of the electronic system is obatined indicating hysteresis behavior. +However, since the total energy is lower for the magnetic result it is believed to constitute the real, i.e. global, minimum with respect to electronic minimization. A low activation energy of \unit[0.1]{eV} is observed for the a$\rightarrow$b transition. Thus, configuration a is very unlikely to occur in favor of configuration b.