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<title>MCCCS Towhee (Kramer-Farragher-van Beest-van Santen)</title>
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<div align="center"> <font size="5"> <b><font face="Arial, Helvetica, sans-serif"><a name="top"></a>MCCCS
Towhee (Kramer-Farragher-van Beest-van Santen)</font></b> </font> </div>
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<p> </p>
<p> </p>
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<td width="697" valign="top"> <b>Overview</b>
<ul>
This section covers the Kramer-Farragher-van Beest-van Santen (KFvBvS)
force field as it is implemented into the towhee_ff_KFvBvS file in the ForceFields directory.
All of the Towhee atom types for the KFvBvS force
field are listed, along with a short description of their meanings.
The KFvBvS force field uses the exponential-6 potential type and therefore
must also use explicit combining rules. It therefore cannot be combined with
other force fields.
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.
<p> </p>
</ul>
<b>References for KFvBvS</b>
<ul>
This force field comes from the work of Kramer, Farragher, van Beest, and van Santen. I created
the name for this force field from the initials of the last names of the authors. The parameters
were taken from the mixed SCF empirical force field listed in
<ul>
<li><a href="../references.html#vanbeest_et_al_1990">van Beest <i>et al.</i> 1990</a></li>
<li><a href="../references.html#kramer_et_al_1991">Kramer <i>et al.</i> 1991</a></li>
</ul>
</ul>
<b>KFvBvS in Towhee</b>
<ul>
The official force field name for these parameters is either 'KFvBvS'. Here I list all of the KFvBvS
atom names for use in the towhee_input file, along with a brief description of what atoms we are talking about.
This force field is intended for use with silacious materials (zeolites, silica, etc.).
For some reason they did not include repulsive potentials between many of the atoms and Cl. Thus, Cl can
only be used in combination with other negative ions, or with Na.
Please note that the capitalization and spacing pattern is important
and must be followed exactly as listed here.
<ul>
<li><b>'Al'</b> : aluminum</li>
<li><b>'Cl'</b> : chlorine</li>
<li><b>'Na'</b> : sodium</li>
<li><b>'O'</b> : oxygen</li>
<li><b>'P'</b> : phosphorous</li>
<li><b>'Si'</b> : silicon</li>
</ul>
</ul>
<b>Coulombic interactions</b>
<ul>
Atom centered point charges are used to represent the electrostatic interactions. Below is a list
of charges taken from the mixed SCF empirical force field in
<a href="../references.html#kramer_et_al_1991">Kramer <i>et al.</i> 1991</a>
<li><b>'Al'</b> : 1.4</li>
<li><b>'Cl'</b> : -1.0</li>
<li><b>'Na'</b> : 1.0</li>
<li><b>'O'</b> : -1.2</li>
<li><b>'P'</b> : 3.4</li>
<li><b>'Si'</b> : 2.4</li>
</ul>
<b>Improper torsions</b>
<ul>
There are no improper torsions in this force field.
</ul>
<b>Proteins</b>
<ul>
The KFvBvS force field is designed for zeolites and is not suited for proteins.
</ul>
<a href="../towhee_capabilities.html">Return to the Towhee Capabilities web page</a>
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<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 -->
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