--- trunk/tengDissertation/LiquidCrystal.tex 2006/06/20 13:46:10 2870 +++ trunk/tengDissertation/LiquidCrystal.tex 2006/06/23 21:33:52 2882 @@ -212,8 +212,8 @@ every banana shaped molecule has been represented thre A series of molecular dynamics simulations were perform to study the phase behavior of banana shaped liquid crystals. In each simulation, -every banana shaped molecule has been represented three GB particles -which is characterized by $\mu = 1,~ \nu = 2, +every banana shaped molecule has been represented by three GB +particles which is characterized by $\mu = 1,~ \nu = 2, ~\epsilon_{e}/\epsilon_{s} = 1/5$ and $\sigma_{e}/\sigma_{s} = 3$. All of the simulations begin with same equilibrated isotropic configuration where 1024 molecules without dipoles were confined in @@ -222,6 +222,8 @@ To investigate the phase structure of the model liquid barostat of 50~ps were used to equilibrate the system to desired temperature and pressure. +\subsection{Order Parameters} + To investigate the phase structure of the model liquid crystal, we calculated various order parameters and correlation functions. Particulary, the $P_2$ order parameter allows us to estimate average @@ -254,26 +256,44 @@ where $X$, $Y$ and $Z$ are axis of the director frame. \end{equation} where $X$, $Y$ and $Z$ are axis of the director frame. +\subsection{Structure Properties} -The density correlation along the director is -\begin{equation}g(z) =< \delta (z-z_{ij})>_{ij} / \pi R^{2} \rho +It is more important to show the density correlation along the +director +\begin{equation} +g(z) =< \delta (z-z_{ij})>_{ij} / \pi R^{2} \rho \end{equation}, -where $z_{ij} = r_{ij} cos \beta_{r_{ij}}$ was measured in the -director frame and $R$ is the radius of the cylindrical sampling -region. +where $z_{ij} = r_{ij} \dot Z$ was measured in the director frame +and $R$ is the radius of the cylindrical sampling region. + +\subsection{Rotational Invariants} + +As a useful set of correlation functions to describe +position-orientation correlation, rotation invariants were first +applied in a spherical symmetric system to study x-ray and light +scatting\cite{Blum1971}. Latterly, expansion of the orientation pair +correlation in terms of rotation invariant for molecules of +arbitrary shape was introduce by Stone\cite{Stone1978} and adopted +by other researchers in liquid crystal studies\cite{Berardi2000}. +\begin{eqnarray} +S_{22}^{220} (r) & = & \frac{1}{{4\sqrt 5 }} \left< \delta (r - +r_{ij} )((\hat x_i \cdot \hat x_j )^2 - (\hat x_i \cdot \hat y_j +)^2 - (\hat y_i \cdot \hat x_j )^2 + (\hat y_i \cdot \hat y_j +)^2 ) \right. \\ + & & \left. - 2(\hat x_i \cdot \hat y_j )(\hat y_i \cdot \hat x_j ) - +2(\hat x_i \cdot \hat x_j )(\hat y_i \cdot \hat y_j )) \right> +\end{eqnarray} +\begin{equation} +S_{00}^{221} (r) = - \frac{{\sqrt 3 }}{{\sqrt {10} }}\left\langle +{\delta (r - r_{ij} )((\hat z_i \cdot \hat z_j )(\hat z_i \cdot +\hat z_j \times \hat r_{ij} ))} \right\rangle +\end{equation} + \section{Results and Conclusion} \label{sec:results and conclusion} To investigate the molecular organization behavior due to different dipolar orientation and position with respect to the center of the molecule, - - - -\section{\label{liquidCrystalSection:methods}Methods} - -\section{\label{liquidCrystalSection:resultDiscussion}Results and Discussion} - -\section{Conclusion}