X-Git-Url: https://hackdaworld.org/gitweb/?p=lectures%2Flatex.git;a=blobdiff_plain;f=posic%2Fthesis%2Fd_tersoff.tex;h=b031be2f58ecd016152de51b4e26e136c23450aa;hp=c01a65eaf34d207e955e3b23b4f2275909113b85;hb=17d5c879c418790a154098e51c524eca183c4d98;hpb=fdf1f976b879c9b7403c1d76c9906aa850614862 diff --git a/posic/thesis/d_tersoff.tex b/posic/thesis/d_tersoff.tex index c01a65e..b031be2 100644 --- a/posic/thesis/d_tersoff.tex +++ b/posic/thesis/d_tersoff.tex @@ -3,7 +3,7 @@ \section{Form of the Tersoff potential and its derivative} -The Tersoff potential \cite{tersoff_m} is of the form +The Tersoff potential~\cite{tersoff_m} is of the form \begin{eqnarray} E & = & \sum_i E_i = \frac{1}{2} \sum_{i \ne j} V_{ij} \textrm{ ,} \\ V_{ij} & = & f_C(r_{ij}) [ f_R(r_{ij}) + b_{ij} f_A(r_{ij}) ] \textrm{ .} @@ -32,13 +32,13 @@ f_C(r_{ij}) = \left\{ 0, & r_{ij} > S_{ij} \end{array} \right. \end{equation} -with $\theta_{ijk}$ being the bond angle between bonds $ij$ and $ik$ as shown in Figure \ref{img:tersoff_angle}.\\ +with $\theta_{ijk}$ being the bond angle between bonds $ij$ and $ik$ as shown in Figure~\ref{img:tersoff_angle}.\\ \\ For a three body potential, if $V_{ij}$ is not equal to $V_{ji}$, the derivative is of the form \begin{equation} \nabla_{{\bf r}_i} E = \frac{1}{2} \big[ \sum_j ( \nabla_{{\bf r}_i} V_{ij} + \nabla_{{\bf r}_i} V_{ji} ) + \sum_k \sum_j \nabla_{{\bf r}_i} V_{jk} \big] \textrm{ .} \end{equation} -In the following all the necessary derivatives to calculate $\nabla_{{\bf r}_i} E$ are written down. +In the following, all the necessary derivatives to calculate $\nabla_{{\bf r}_i} E$ are written down. \section[Derivative of $V_{ij}$ with respect to ${r}_i$]{\boldmath Derivative of $V_{ij}$ with respect to ${\bf r}_i$} @@ -138,7 +138,7 @@ are calculated and added in subsequent loops. b_{ij} \nabla_{{\bf r}_j} f_A(r_{ij}) + f_A(r_{ij}) \nabla_{{\bf r}_j} b_{ij} \big] \end{eqnarray} -Using the equality $\nabla_{{\bf r}_i} r_{ij}=-\nabla_{{\bf r}_j} r_{ij}$ +Using the equality $\nabla_{{\bf r}_i} r_{ij}=-\nabla_{{\bf r}_j} r_{ij}$, the following relations are valid: \begin{eqnarray} \nabla_{{\bf r}_j} f_R(r_{ij}) &=& - \nabla_{{\bf r}_i} f_R(r_{ij}) \\ @@ -185,7 +185,7 @@ Concerning $b_{ij}$, in addition to the angular term, the derivative of the cut- \subsection{Code realization} -The implementation of the force evaluation shown in the following is applied to the potential designed by Erhart and Albe \cite{albe_sic_pot}. +The implementation of the force evaluation shown in the following is applied to the potential designed by Erhart and Albe~\cite{albe_sic_pot}. There are slight differences compared to the original potential by Tersoff: \begin{itemize} \item Difference in sign of the attractive part.