<ForceField>
 <Info>
  <DateGenerated>2022-06-21</DateGenerated>
  <Reference>Izadi S, Anandakrishnan R, Onufriev AV. Building Water Models: A Different Approach. The Journal of Physical Chemistry Letters. 2014 Nov 6;5(21):3863-71. DOI:10.1021/jz501780a</Reference>
 </Info>
 <AtomTypes>
  <Type name="opc-O" class="OW" element="O" mass="16.00000"/>
  <Type name="opc-H" class="HW" element="H" mass="1.00800"/>
  <Type name="opc-M" class="MW" mass="0"/>
 </AtomTypes>
 <Residues>
  <Residue name="HOH">
   <Atom name="O" type="opc-O"/>
   <Atom name="H1" type="opc-H"/>
   <Atom name="H2" type="opc-H"/>
   <Atom name="M" type="opc-M"/>
   <!-- weight2 = 0.15939833/(2*(cos(angle/2) * 0.87243313)) -->
   <VirtualSite type="average3" index="3" atom1="0" atom2="1" atom3="2" weight1="0.7045587810585758" weight2="0.1477206094707121" weight3="0.1477206094707121"/>
   <Bond from="0" to="1"/>
   <Bond from="0" to="2"/>
  </Residue>
 </Residues>
 <HarmonicBondForce>
  <Bond class1="OW" class2="HW" length="0.087243313" k="502416.0"/>
 </HarmonicBondForce>
 <HarmonicAngleForce>
  <!-- angle = arccos(1 - (1.37120510**2 / (2*0.87243313**2))) -->
  <Angle class1="HW" class2="OW" class3="HW" angle="1.8081424254418306" k="628.02"/>
 </HarmonicAngleForce>
 <NonbondedForce coulomb14scale="0.833333" lj14scale="0.5">
  <!-- sigma = (1.777167268 * 2 / (2**(1/6)))*unit.angstrom/unit.nanometer -->
  <!-- epsilon = (0.2128008130*unit.kilocalorie)/(unit.kilojoule) -->
  <Atom type="opc-O" charge="0" sigma="0.3166552081964338" epsilon="0.8903586015920001"/>
  <Atom type="opc-H" charge="0.679142" sigma="0.08908987181403394" epsilon="0"/>
  <Atom type="opc-M" charge="-1.358284" sigma="0.08908987181403394" epsilon="0"/>
 </NonbondedForce>
</ForceField>
