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<p>Dear gmx'ers,</p>
<p><br></p>
<p>Inspecting gromacs' OPLSAA files, I find here two atom types for argon. File ffoplsaa.atp includes:</p>
<p> opls_097 39.94800 ; Argon from Verlet & Weis Mol.Phys.,24,1013 (1972) </p>
<p>and</p>
<p> Ar 39.948 ; Argon</p>
<p><br></p>
<p>LJ parameters are (file ffoplsaanb.itp):</p>
<p>[ atomtypes ]</p>
<p>; name bond_type mass charge ptype sigma epsilon</p>
<p> opls_097 Ar 18 39.94800 0.000 A 3.40100e-01 9.78638e-01 ; SIG</p>
<p>...</p>
<p> Ar Ar 18 39.94800 0.000 A 3.41000e-01 2.74580e-02</p>
<p><br></p>
<p>The first set looks somewhat like the real Ar--Ar pair potential. </p>
<p>A short comment before the second set says:</p>
<p>; These ion atomtypes are NOT part of OPLS, but since they are</p>
<p>; needed for some proteins or tutorial Argon simulations we have added them.</p>
<p><br></p>
<p>But its well depth is extremely low! What simulations is this set intended for?</p>
<p><span class=rvts6>-- </span></p>
<p><span class=rvts6>Regards,</span></p>
<p><span class=rvts6> Dmitri </span><a class=rvts7 href="mailto:ddubov@ngs.ru">mailto:ddubov@ngs.ru</a></p>
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