<html> <head> <title>MCCCS Towhee (TraPPE Explicit Hydrogen)</title> </head> <body bgcolor="#FFFFFF" text="#000000"> <table width="675" border="0" cellspacing="0" cellpadding="0" height="590"> <tr> <td colspan="2" height="29"> <div align="center"> <font size="5"> <b><font face="Arial, Helvetica, sans-serif"><a name="top"></a>MCCCS Towhee (TraPPE Explict Hydrogen)</font></b> </font> </div> </td> </tr> <A href="http://sourceforge.net"> <IMG src="http://sourceforge.net/sflogo.php?group_id=87039&type=5" width="210" height="62" border="0" alt="SourceForge.net Logo" align="right"/> </A> <tr> <td width="18" height="371" valign="top"> <p> </p> <p> </p> </td> <td width="697" valign="top"> <b>Overview</b> <ul> This section covers the TraPPE Explicit Hydrogen (TraPPE-EH) force field as it is implemented into the towhee_ff_TraPPE-EH file in the ForceFields directory. All of the Towhee atom types for the TraPPE Explicit Hydrogen force field are listed, along with a short description of their meanings. For more information about the TraPPE family of force fields see the <a href="http://siepmann6.chem.umn.edu/">Siepmann group web site</a>. Note that TraPPE-EH is a Lennard-Jones (12-6) force field and can only be combined with other Lennard-Jones (12-6) force fields. It is particularily suitable for combination with the <a href="trappeua.html">TraPPE United Atom</a> force field. Any discrepencies (especially typos) from the published force field values are the sole responsibility of Marcus G. Martin, and I welcome feedback on how this implementation compares with other programs. </ul> <b>References for TraPPE-EH</b> <ul> TraPPE-EH is still under development by the Siepmann group. The current implementation includes only a subset of the total published parameters. Here is the current list of references. <ul> <li><a href="../references.html#potoff_siepmann_2001">Potoff and Siepmann 2001</a></li> </ul> </ul> <b>TraPPE-EH in Towhee</b> <ul> The official force field name for TraPPE Explicit Hydrogen in Towhee is 'TraPPE-EH'. Here I list all of the TraPPE-EH atom names for use in the towhee_input file, along with a brief description. I created these atom names in order to work with the molecule assembler. Please note that the capitalization and spacing pattern is important and must be followed exactly as listed here. <ul> <dt><font color="red">Carbon Dioxide</font></dt> <li><b>'C_co2'</b> : central carbon in carbon dioxide.</li> <li><b>'O_co2'</b> : oxygen in carbon dioxide.</li> <dt><font color="red">N<sub>2</sub></font></dt> <li><b>'N_n2'</b> : nitrogen atom in N<sub>2</sub>.</li> <li><b>'COM_n2'</b> : center of mass in N<sub>2</sub>. This molecule is treated as a three site model with both of the nitrogen atoms bonded to the center-of-mass.</li> </ul> </ul> <b>Coulombic interactions</b> <ul> TraPPE-EH uses atom-centered, and other interaction site centered, point charges to represent the electrostatic interactions. The 'bond increment' method for assigning charges is implemented for these molecules. Please see the <a href="../inpstyle/inpstyle_2.html">inpstyle 2</a> documentation for further information on enabling this option. Here I list the bond increments for the atom names listed above. The value of the bond increment is added to the first atom listed and subtracted from the second atom listed. <ul> <li><font color="green">O_co2</font> - <font color="green">O_co2</font>: -0.35</li> <li><font color="green">N_n2</font> - <font color="green">COM_n2</font>: -0.482</li> </ul> </ul> <b>Improper torsions</b> <ul> TraPPE-EH does not utilize improper torsions. </ul> <a href="../towhee_capabilities.html">Return to the Towhee Capabilities web page</a> <p> </p> </td> </tr> </table> <hr width="715" align="left"> <i><font size="2">Send comments to:</font></i> <font size="2"> <a href="mailto:marcus_martin@users.sourceforge.net">Marcus G. Martin</a><br> <i>Last updated:</i> <!-- #BeginDate format:Am1 -->September 07, 2005<!-- #EndDate --> </font> <br> </body> </html>