ForceField support TIP4P and TIP5P

platforms/opencl/src/kernels/removeCM.cl

@@ -7,6 +7,7 @@ __kernel void calcCenterOfMassMomentum(int numAtoms, __global const float4* rest
     float4 cm = 0.0f;
     while (index < numAtoms) {
         float4 velocity = velm[index];
+        if (velocity.w != 0.0)
             cm.xyz += velocity.xyz/velocity.w;
         index += get_global_size(0);
     }

wrappers/python/simtk/openmm/app/data/pdbNames.xml

@@ -269,7 +269,7 @@
   <Atom name="H72" alt1="2H5M"/>
   <Atom name="H73" alt1="3H5M"/>
  </Residue>
- <Residue name="HOH" alt1="H20" alt2="WAT">
+ <Residue name="HOH" alt1="H20" alt2="WAT" alt3="SOL">
   <Atom name="O" alt1="OW"/>
   <Atom name="H1" alt1="HW1"/>
   <Atom name="H2" alt1="HW2"/>

wrappers/python/simtk/openmm/app/data/tip4p.xml

+<ForceField>
+ <AtomTypes>
+  <Type name="tip4p-O" class="OW" element="O" mass="15.99943"/>
+  <Type name="tip4p-H" class="HW" element="H" mass="1.007947"/>
+  <Type name="tip4p-M" class="MW" mass="0"/>
+ </AtomTypes>
+ <Residues>
+  <Residue name="HOH">
+   <Atom name="O" type="tip4p-O"/>
+   <Atom name="H1" type="tip4p-H"/>
+   <Atom name="H2" type="tip4p-H"/>
+   <Atom name="M" type="tip4p-M"/>
+   <VirtualSite type="average3" index="3" atom1="0" atom2="1" atom3="2" weight1="0.74397587" weight2="0.128012065" weight3="0.128012065"/>
+   <Bond from="0" to="1"/>
+   <Bond from="0" to="2"/>
+  </Residue>
+ </Residues>
+ <HarmonicBondForce>
+  <Bond class1="OW" class2="HW" length="0.09572" k="462750.4"/>
+ </HarmonicBondForce>
+ <HarmonicAngleForce>
+  <Angle class1="HW" class2="OW" class3="HW" angle="1.82421813418" k="836.8"/>
+ </HarmonicAngleForce>
+ <NonbondedForce coulomb14scale="0.833333" lj14scale="0.5">
+  <Atom type="tip4p-O" charge="0" sigma="0.315365" epsilon="0.64852"/>
+  <Atom type="tip4p-H" charge="0.52" sigma="1" epsilon="0"/>
+  <Atom type="tip4p-M" charge="-1.04" sigma="1" epsilon="0"/>
+ </NonbondedForce>
+</ForceField>
+

wrappers/python/simtk/openmm/app/data/tip5p.xml

+<ForceField>
+ <AtomTypes>
+  <Type name="tip5p-O" class="OW" element="O" mass="15.99943"/>
+  <Type name="tip5p-H" class="HW" element="H" mass="1.007947"/>
+  <Type name="tip5p-M" class="MW" mass="0"/>
+ </AtomTypes>
+ <Residues>
+  <Residue name="HOH">
+   <Atom name="O" type="tip5p-O"/>
+   <Atom name="H1" type="tip5p-H"/>
+   <Atom name="H2" type="tip5p-H"/>
+   <Atom name="M1" type="tip5p-M"/>
+   <Atom name="M2" type="tip5p-M"/>
+   <VirtualSite type="outOfPlane" index="3" atom1="0" atom2="1" atom3="2" weight12="-0.34490826" weight13="-0.34490826" weightCross="-6.4437903"/>
+   <VirtualSite type="outOfPlane" index="4" atom1="0" atom2="1" atom3="2" weight12="-0.34490826" weight13="-0.34490826" weightCross="6.4437903"/>
+   <Bond from="0" to="1"/>
+   <Bond from="0" to="2"/>
+  </Residue>
+ </Residues>
+ <HarmonicBondForce>
+  <Bond class1="OW" class2="HW" length="0.09572" k="462750.4"/>
+ </HarmonicBondForce>
+ <HarmonicAngleForce>
+  <Angle class1="HW" class2="OW" class3="HW" angle="1.82421813418" k="836.8"/>
+ </HarmonicAngleForce>
+ <NonbondedForce coulomb14scale="0.833333" lj14scale="0.5">
+  <Atom type="tip5p-O" charge="0" sigma="0.312" epsilon="0.66944"/>
+  <Atom type="tip5p-H" charge="0.241" sigma="1" epsilon="0"/>
+  <Atom type="tip5p-M" charge="-0.241" sigma="1" epsilon="0"/>
+ </NonbondedForce>
+</ForceField>
+

wrappers/python/simtk/openmm/app/forcefield.py

@@ -57,7 +57,10 @@ class ForceField(object):
             
             if tree.getroot().find('AtomTypes') is not None:
                 for type in tree.getroot().find('AtomTypes').findall('Type'):
-                    self._atomTypes[type.attrib['name']] = (type.attrib['class'], float(type.attrib['mass']), elem.get_by_symbol(type.attrib['element']))
+                    element = None
+                    if 'element' in type.attrib:
+                        element = elem.get_by_symbol(type.attrib['element'])
+                    self._atomTypes[type.attrib['name']] = (type.attrib['class'], float(type.attrib['mass']), element)
             
             # Load the residue templates.
             
@@ -68,6 +71,8 @@ class ForceField(object):
                     self._templates[resName] = template
                     for atom in residue.findall('Atom'):
                         template.atoms.append(ForceField._TemplateAtomData(atom.attrib['name'], atom.attrib['type'], self._atomTypes[atom.attrib['type']][2]))
+                    for site in residue.findall('VirtualSite'):
+                        template.virtualSites.append(ForceField._VirtualSiteData(site))
                     for bond in residue.findall('Bond'):
                         b = (int(bond.attrib['from']), int(bond.attrib['to']))
                         template.bonds.append(b)
@@ -79,6 +84,9 @@ class ForceField(object):
                         template.atoms[b].externalBonds += 1
             for template in self._templates.values():
                 template.signature = _createResidueSignature([atom.element for atom in template.atoms])
+                if template.signature is None:
+                    sigString = None
+                else:
                     sigString = _signatureToString(template.signature)
                 if sigString in self._templateSignatures:
                     self._templateSignatures[sigString].append(template)
@@ -144,6 +152,7 @@ class ForceField(object):
         def __init__(self):
             self.atomType = {}
             self.atoms = []
+            self.virtualSites = {}
             self.bonds = []
             self.angles = []
             self.propers = []
@@ -156,6 +165,7 @@ class ForceField(object):
         def __init__(self, name):
             self.name = name
             self.atoms = []
+            self.virtualSites = []
             self.bonds = []
             self.externalBonds = []
 
@@ -176,6 +186,25 @@ class ForceField(object):
             self.isConstrained = False
             self.length = 0.0
     
+    class _VirtualSiteData:
+        """Inner class used to encapsulate data about a virtual site."""
+        def __init__(self, node):
+            attrib = node.attrib
+            self.index = int(attrib['index'])
+            self.type = attrib['type']
+            if self.type == 'average2':
+                self.atoms = [int(attrib['atom1']), int(attrib['atom2'])]
+                self.weights = [float(attrib['weight1']), float(attrib['weight2'])]
+            elif self.type == 'average3':
+                self.atoms = [int(attrib['atom1']), int(attrib['atom2']), int(attrib['atom3'])]
+                self.weights = [float(attrib['weight1']), float(attrib['weight2']), float(attrib['weight3'])]
+            elif self.type == 'outOfPlane':
+                self.atoms = [int(attrib['atom1']), int(attrib['atom2']), int(attrib['atom3'])]
+                self.weights = [float(attrib['weight12']), float(attrib['weight13']), float(attrib['weightCross'])]
+            else:
+                raise ValueError('Unknown virtual site type: %s' % self.type)
+            self.atoms = [x-self.index for x in self.atoms]
+
     def createSystem(self, topology, nonbondedMethod=NoCutoff, nonbondedCutoff=1.0*unit.nanometer,
                      constraints=None, rigidWater=True, removeCMMotion=True, **args):
         """Construct an OpenMM System representing a Topology with this force field.
@@ -225,19 +254,31 @@ class ForceField(object):
         
         for chain in topology.chains():
             for res in chain.residues():
-                signature = _signatureToString(_createResidueSignature([atom.element for atom in res.atoms()]))
                 template = None
                 matches = None
+                sig = _createResidueSignature([atom.element for atom in res.atoms()])
+                if sig is not None:
+                    signature = _signatureToString(sig)
                     if signature in self._templateSignatures:
                         for t in self._templateSignatures[signature]:
                             matches = _matchResidue(res, t, bondedToAtom, atomIndices)
                             if matches is not None:
                                 template = t
                                 break
+                if matches is None:
+                    # Check templates involving virtual sites
+                    for t in self._templateSignatures[None]:
+                        matches = _matchResidue(res, t, bondedToAtom, atomIndices)
+                        if matches is not None:
+                            template = t
+                            break
                 if matches is None:
                     raise ValueError('No template found for residue %d (%s)' % (res.index+1, res.name))
                 for atom, match in zip(res.atoms(), matches):
                     data.atomType[atom] = template.atoms[match].type
+                    for site in template.virtualSites:
+                        if match == site.index:
+                            data.virtualSites[atom] = site
 
         # Create the System and add atoms
         
@@ -338,6 +379,18 @@ class ForceField(object):
                 if atom1.residue.name == 'HOH' and atom2.residue.name == 'HOH' and atom3.residue.name == 'HOH':
                     data.isAngleConstrained[i] = True
         
+        # Add virtual sites
+        
+        for atom in data.virtualSites:
+            site = data.virtualSites[atom]
+            index = atomIndices[atom]
+            if site.type == 'average2':
+                sys.setVirtualSite(index, mm.TwoParticleAverageSite(index+site.atoms[0], index+site.atoms[1], site.weights[0], site.weights[1]))
+            elif site.type == 'average3':
+                sys.setVirtualSite(index, mm.ThreeParticleAverageSite(index+site.atoms[0], index+site.atoms[1], index+site.atoms[2], site.weights[0], site.weights[1], site.weights[2]))
+            elif site.type == 'outOfPlane':
+                sys.setVirtualSite(index, mm.OutOfPlaneSite(index+site.atoms[0], index+site.atoms[1], index+site.atoms[2], site.weights[0], site.weights[1], site.weights[2]))
+        
         # Add forces to the System
         
         for force in self._forces:
@@ -351,6 +404,8 @@ def _createResidueSignature(elements):
     """Create a signature for a residue based on the elements of the atoms it contains."""
     counts = {}
     for element in elements:
+        if element is None:
+            return None # This residue contains "atoms" (probably virtual sites) that should match any element
         if element in counts:
             counts[element] += 1
         else:
@@ -382,6 +437,8 @@ def _matchResidue(res, template, bondedToAtom, atomIndices):
     or None if it does not match the template
     """
     atoms = list(res.atoms())
+    if len(atoms) != len(template.atoms):
+        return None
     residueAtomBonds = []
     templateAtomBonds = []
     matches = len(atoms)*[0]
@@ -410,7 +467,7 @@ def _findAtomMatches(atoms, template, bondedTo, externalBonds, matches, hasMatch
     elem = atoms[position].element
     for i in range(len(atoms)):
         atom = template.atoms[i]
-        if atom.element == elem and not hasMatch[i] and len(atom.bondedTo) == len(bondedTo[position]) and atom.externalBonds == externalBonds[position]:
+        if (atom.element == elem or atom.element is None) and not hasMatch[i] and len(atom.bondedTo) == len(bondedTo[position]) and atom.externalBonds == externalBonds[position]:
             # See if the bonds for this identification are consistent
             
             allBondsMatch = all((bonded > position or matches[bonded] in atom.bondedTo for bonded in bondedTo[position]))
@@ -869,9 +926,15 @@ class NonbondedGenerator:
                 force.addParticle(values[0], values[1], values[2])
             else:
                 raise ValueError('No nonbonded parameters defined for atom type '+t)
+        # Create exceptions based on bonds and virtual sites.
         bondIndices = []
         for bond in data.bonds:
             bondIndices.append((bond.atom1, bond.atom2))
+        for i in range(sys.getNumParticles()):
+            if sys.isVirtualSite(i):
+                site = sys.getVirtualSite(i)
+                for j in range(site.getNumParticles()):
+                    bondIndices.append((i, site.getParticle(j)))
         force.createExceptionsFromBonds(bondIndices, self.coulomb14scale, self.lj14scale)
         force.setNonbondedMethod(methodMap[nonbondedMethod])
         force.setCutoffDistance(nonbondedCutoff)

wrappers/python/src/swig_doxygen/swigInputConfig.py

@@ -173,6 +173,7 @@ NO_OUTPUT_ARGS = [('LocalEnergyMinimizer', 'minimize', 'context'),
 # The list is the argument position(s).
 STEAL_OWNERSHIP = {("Platform", "registerPlatform") : [0],
                    ("System", "addForce") : [0],
+                   ("System", "setVirtualSite") : [1],
 }
 
 # This is a list of units to attach to return values and method args.