<div>Hello everyone,</div>
<div> </div>
<div>I am trying to include a POPC 53a6 topology from LipidsForGro96_53a6.zip ( <a href="http://www.gromacs.org/index.php?title=Download_%26_Installation/User_contributions/Molecule_topologies" target="_blank"><font color="#2a5db0">http://www.gromacs.org/index.php?title=Download_%26_Installation/User_contributions/Molecule_topologies</font></a> ) for a simple lipid in water sim (gromacs version 4.0.5).</div>
<div> </div>
<div>I am using the lipid coordinates from the same archive and here's my topology:</div>
<div>***</div>
<div>#include "ffG53a6.itp"</div>
<div>#include "popc_53a6.itp"</div>
<div>#include "spc.itp"</div>
<div> </div>
<div>[ system ]</div>
<div>;Name</div>
<div>test</div>
<div> </div>
<div>[ molecules ]</div>
<div>POPC 128</div>
<div>SOL 3585</div>
<div>***</div>
<div> </div>
<div>grompp throws a fatal error: " Value of 'multiplicity' in Proper Dih. is 0, which is smaller than the minimum of 1" without any prior warnings. </div>
<div>The error has to do with two dihedral angles with zero multiplicity:</div>
<div> </div>
<div>...</div>
<div>22 23 24 25 1 90 -5.685 0</div>
<div>...</div>
<div>24 25 26 27 1 90 -5.685 0</div>
<div>...</div>
<div> </div>
<div>So I looked at an ancient POPC topology for GROMOS87 and these dihedrals have zero equilibrium angle and a multiplicity of 3:</div>
<div> </div>
<div>
<div>...</div>
<div>22 23 24 25 1 0.0 5.858 3</div>
<div>...</div>
<div>24 25 26 27 1 0.0 5.858 3</div>
<div>...</div>
<div> </div>
<div>Did the author of the 53a6 topology want to simply remove these dihedrals by setting a multiplicity of zero? Or, should these two be set according to the older topology? I know similar questions have been asked here in the past, but I really want to make sure my topology is sane. Thanks a lot.</div>
<div> </div>
<div>Alex</div></div>