Add check for consistent force field/solvent model version

wrappers/python/openmm/app/data/charmm36.xml

@@ -103763,4 +103763,12 @@
     <NBFixPair epsilon="0.8631592000000001" sigma="0.25134925534893393" type1="MG" type2="SO"/>
     <NBFixPair epsilon="0.8414024" sigma="0.25219560913116723" type1="MG" type2="SS1"/>
   </LennardJonesForce>
+  <InitializationScript>
+EXPECTED_VERSION = "charmm36"
+if hasattr(self, "_charmm_ff_version"):
+    if self._charmm_ff_version != EXPECTED_VERSION:
+        raise RuntimeError(f"CHARMM force field versions ({self._charmm_ff_version} and {EXPECTED_VERSION}) incompatible")
+else:
+    self._charmm_ff_version = EXPECTED_VERSION
+  </InitializationScript>
 </ForceField>

wrappers/python/openmm/app/data/charmm36/spce.xml

@@ -121,4 +121,12 @@
     <NBFixPair epsilon="0.31388368000000005" sigma="0.28419669108676826" type1="OC2D2" type2="SOD"/>
     <NBFixPair epsilon="0.31388368000000005" sigma="0.28419669108676826" type1="OG2D2" type2="SOD"/>
   </LennardJonesForce>
+  <InitializationScript>
+EXPECTED_VERSION = "charmm36"
+if hasattr(self, "_charmm_ff_version"):
+    if self._charmm_ff_version != EXPECTED_VERSION:
+        raise RuntimeError(f"CHARMM force field versions ({self._charmm_ff_version} and {EXPECTED_VERSION}) incompatible")
+else:
+    self._charmm_ff_version = EXPECTED_VERSION
+  </InitializationScript>
 </ForceField>

wrappers/python/openmm/app/data/charmm36/tip3p-pme-b.xml

@@ -121,4 +121,12 @@
     <NBFixPair epsilon="0.31388368000000005" sigma="0.28419669108676826" type1="OC2D2" type2="SOD"/>
     <NBFixPair epsilon="0.31388368000000005" sigma="0.28419669108676826" type1="OG2D2" type2="SOD"/>
   </LennardJonesForce>
+  <InitializationScript>
+EXPECTED_VERSION = "charmm36"
+if hasattr(self, "_charmm_ff_version"):
+    if self._charmm_ff_version != EXPECTED_VERSION:
+        raise RuntimeError(f"CHARMM force field versions ({self._charmm_ff_version} and {EXPECTED_VERSION}) incompatible")
+else:
+    self._charmm_ff_version = EXPECTED_VERSION
+  </InitializationScript>
 </ForceField>

wrappers/python/openmm/app/data/charmm36/tip3p-pme-f.xml

@@ -121,4 +121,12 @@
     <NBFixPair epsilon="0.31388368000000005" sigma="0.28419669108676826" type1="OC2D2" type2="SOD"/>
     <NBFixPair epsilon="0.31388368000000005" sigma="0.28419669108676826" type1="OG2D2" type2="SOD"/>
   </LennardJonesForce>
+  <InitializationScript>
+EXPECTED_VERSION = "charmm36"
+if hasattr(self, "_charmm_ff_version"):
+    if self._charmm_ff_version != EXPECTED_VERSION:
+        raise RuntimeError(f"CHARMM force field versions ({self._charmm_ff_version} and {EXPECTED_VERSION}) incompatible")
+else:
+    self._charmm_ff_version = EXPECTED_VERSION
+  </InitializationScript>
 </ForceField>

wrappers/python/openmm/app/data/charmm36/tip4p2005.xml

@@ -127,4 +127,12 @@
     <NBFixPair epsilon="0.31388368000000005" sigma="0.28419669108676826" type1="OC2D2" type2="SOD"/>
     <NBFixPair epsilon="0.31388368000000005" sigma="0.28419669108676826" type1="OG2D2" type2="SOD"/>
   </LennardJonesForce>
+  <InitializationScript>
+EXPECTED_VERSION = "charmm36"
+if hasattr(self, "_charmm_ff_version"):
+    if self._charmm_ff_version != EXPECTED_VERSION:
+        raise RuntimeError(f"CHARMM force field versions ({self._charmm_ff_version} and {EXPECTED_VERSION}) incompatible")
+else:
+    self._charmm_ff_version = EXPECTED_VERSION
+  </InitializationScript>
 </ForceField>

wrappers/python/openmm/app/data/charmm36/tip4pew.xml

@@ -127,4 +127,12 @@
     <NBFixPair epsilon="0.31388368000000005" sigma="0.28419669108676826" type1="OC2D2" type2="SOD"/>
     <NBFixPair epsilon="0.31388368000000005" sigma="0.28419669108676826" type1="OG2D2" type2="SOD"/>
   </LennardJonesForce>
+  <InitializationScript>
+EXPECTED_VERSION = "charmm36"
+if hasattr(self, "_charmm_ff_version"):
+    if self._charmm_ff_version != EXPECTED_VERSION:
+        raise RuntimeError(f"CHARMM force field versions ({self._charmm_ff_version} and {EXPECTED_VERSION}) incompatible")
+else:
+    self._charmm_ff_version = EXPECTED_VERSION
+  </InitializationScript>
 </ForceField>

wrappers/python/openmm/app/data/charmm36/tip5p.xml

@@ -129,4 +129,12 @@
     <NBFixPair epsilon="0.31388368000000005" sigma="0.28419669108676826" type1="OC2D2" type2="SOD"/>
     <NBFixPair epsilon="0.31388368000000005" sigma="0.28419669108676826" type1="OG2D2" type2="SOD"/>
   </LennardJonesForce>
+  <InitializationScript>
+EXPECTED_VERSION = "charmm36"
+if hasattr(self, "_charmm_ff_version"):
+    if self._charmm_ff_version != EXPECTED_VERSION:
+        raise RuntimeError(f"CHARMM force field versions ({self._charmm_ff_version} and {EXPECTED_VERSION}) incompatible")
+else:
+    self._charmm_ff_version = EXPECTED_VERSION
+  </InitializationScript>
 </ForceField>

wrappers/python/openmm/app/data/charmm36/tip5pew.xml

@@ -129,4 +129,12 @@
     <NBFixPair epsilon="0.31388368000000005" sigma="0.28419669108676826" type1="OC2D2" type2="SOD"/>
     <NBFixPair epsilon="0.31388368000000005" sigma="0.28419669108676826" type1="OG2D2" type2="SOD"/>
   </LennardJonesForce>
+  <InitializationScript>
+EXPECTED_VERSION = "charmm36"
+if hasattr(self, "_charmm_ff_version"):
+    if self._charmm_ff_version != EXPECTED_VERSION:
+        raise RuntimeError(f"CHARMM force field versions ({self._charmm_ff_version} and {EXPECTED_VERSION}) incompatible")
+else:
+    self._charmm_ff_version = EXPECTED_VERSION
+  </InitializationScript>
 </ForceField>

wrappers/python/openmm/app/data/charmm36/water.xml

@@ -127,4 +127,12 @@
     <NBFixPair epsilon="0.31388368000000005" sigma="0.2877602859593296" type1="OG2D2" type2="SOD"/>
     <NBFixPair epsilon="0.31388368000000005" sigma="0.28152399493234725" type1="OG2P1" type2="SOD"/>
   </LennardJonesForce>
+  <InitializationScript>
+EXPECTED_VERSION = "charmm36"
+if hasattr(self, "_charmm_ff_version"):
+    if self._charmm_ff_version != EXPECTED_VERSION:
+        raise RuntimeError(f"CHARMM force field versions ({self._charmm_ff_version} and {EXPECTED_VERSION}) incompatible")
+else:
+    self._charmm_ff_version = EXPECTED_VERSION
+  </InitializationScript>
 </ForceField>

wrappers/python/openmm/app/data/charmm36_2024.xml

@@ -259418,4 +259418,12 @@ if harmonic_impropers:
         harmonic_force.addTorsion(*improper)
     sys.addForce(harmonic_force)</Script>
+  <InitializationScript>
+EXPECTED_VERSION = "charmm36_2024"
+if hasattr(self, "_charmm_ff_version"):
+    if self._charmm_ff_version != EXPECTED_VERSION:
+        raise RuntimeError(f"CHARMM force field versions ({self._charmm_ff_version} and {EXPECTED_VERSION}) incompatible")
+else:
+    self._charmm_ff_version = EXPECTED_VERSION
+  </InitializationScript>
 </ForceField>
\ No newline at end of file

wrappers/python/openmm/app/data/charmm36_2024/spce.xml

@@ -449,4 +449,12 @@
     <NBFixPair class1="OC2D2" class2="SOD" epsilon="0.31388368000000005" sigma="0.28419669108676826" />
     <NBFixPair class1="OG2D2" class2="SOD" epsilon="0.31388368000000005" sigma="0.28419669108676826" />
   </LennardJonesForce>
+  <InitializationScript>
+EXPECTED_VERSION = "charmm36_2024"
+if hasattr(self, "_charmm_ff_version"):
+    if self._charmm_ff_version != EXPECTED_VERSION:
+        raise RuntimeError(f"CHARMM force field versions ({self._charmm_ff_version} and {EXPECTED_VERSION}) incompatible")
+else:
+    self._charmm_ff_version = EXPECTED_VERSION
+  </InitializationScript>
 </ForceField>
\ No newline at end of file

wrappers/python/openmm/app/data/charmm36_2024/tip3p-pme-b.xml

@@ -449,4 +449,12 @@
     <NBFixPair class1="OC2D2" class2="SOD" epsilon="0.31388368000000005" sigma="0.28419669108676826" />
     <NBFixPair class1="OG2D2" class2="SOD" epsilon="0.31388368000000005" sigma="0.28419669108676826" />
   </LennardJonesForce>
+  <InitializationScript>
+EXPECTED_VERSION = "charmm36_2024"
+if hasattr(self, "_charmm_ff_version"):
+    if self._charmm_ff_version != EXPECTED_VERSION:
+        raise RuntimeError(f"CHARMM force field versions ({self._charmm_ff_version} and {EXPECTED_VERSION}) incompatible")
+else:
+    self._charmm_ff_version = EXPECTED_VERSION
+  </InitializationScript>
 </ForceField>
\ No newline at end of file

wrappers/python/openmm/app/data/charmm36_2024/tip3p-pme-f.xml

@@ -449,4 +449,12 @@
     <NBFixPair class1="OC2D2" class2="SOD" epsilon="0.31388368000000005" sigma="0.28419669108676826" />
     <NBFixPair class1="OG2D2" class2="SOD" epsilon="0.31388368000000005" sigma="0.28419669108676826" />
   </LennardJonesForce>
+  <InitializationScript>
+EXPECTED_VERSION = "charmm36_2024"
+if hasattr(self, "_charmm_ff_version"):
+    if self._charmm_ff_version != EXPECTED_VERSION:
+        raise RuntimeError(f"CHARMM force field versions ({self._charmm_ff_version} and {EXPECTED_VERSION}) incompatible")
+else:
+    self._charmm_ff_version = EXPECTED_VERSION
+  </InitializationScript>
 </ForceField>
\ No newline at end of file

wrappers/python/openmm/app/data/charmm36_2024/tip4p2005.xml

@@ -455,4 +455,12 @@
     <NBFixPair class1="OC2D2" class2="SOD" epsilon="0.31388368000000005" sigma="0.28419669108676826" />
     <NBFixPair class1="OG2D2" class2="SOD" epsilon="0.31388368000000005" sigma="0.28419669108676826" />
   </LennardJonesForce>
+  <InitializationScript>
+EXPECTED_VERSION = "charmm36_2024"
+if hasattr(self, "_charmm_ff_version"):
+    if self._charmm_ff_version != EXPECTED_VERSION:
+        raise RuntimeError(f"CHARMM force field versions ({self._charmm_ff_version} and {EXPECTED_VERSION}) incompatible")
+else:
+    self._charmm_ff_version = EXPECTED_VERSION
+  </InitializationScript>
 </ForceField>
\ No newline at end of file

wrappers/python/openmm/app/data/charmm36_2024/tip4pew.xml

@@ -455,4 +455,12 @@
     <NBFixPair class1="OC2D2" class2="SOD" epsilon="0.31388368000000005" sigma="0.28419669108676826" />
     <NBFixPair class1="OG2D2" class2="SOD" epsilon="0.31388368000000005" sigma="0.28419669108676826" />
   </LennardJonesForce>
+  <InitializationScript>
+EXPECTED_VERSION = "charmm36_2024"
+if hasattr(self, "_charmm_ff_version"):
+    if self._charmm_ff_version != EXPECTED_VERSION:
+        raise RuntimeError(f"CHARMM force field versions ({self._charmm_ff_version} and {EXPECTED_VERSION}) incompatible")
+else:
+    self._charmm_ff_version = EXPECTED_VERSION
+  </InitializationScript>
 </ForceField>
\ No newline at end of file

wrappers/python/openmm/app/data/charmm36_2024/tip5p.xml

@@ -458,4 +458,12 @@
     <NBFixPair class1="OC2D2" class2="SOD" epsilon="0.31388368000000005" sigma="0.28419669108676826" />
     <NBFixPair class1="OG2D2" class2="SOD" epsilon="0.31388368000000005" sigma="0.28419669108676826" />
   </LennardJonesForce>
+  <InitializationScript>
+EXPECTED_VERSION = "charmm36_2024"
+if hasattr(self, "_charmm_ff_version"):
+    if self._charmm_ff_version != EXPECTED_VERSION:
+        raise RuntimeError(f"CHARMM force field versions ({self._charmm_ff_version} and {EXPECTED_VERSION}) incompatible")
+else:
+    self._charmm_ff_version = EXPECTED_VERSION
+  </InitializationScript>
 </ForceField>
\ No newline at end of file

wrappers/python/openmm/app/data/charmm36_2024/tip5pew.xml

@@ -458,4 +458,12 @@
     <NBFixPair class1="OC2D2" class2="SOD" epsilon="0.31388368000000005" sigma="0.28419669108676826" />
     <NBFixPair class1="OG2D2" class2="SOD" epsilon="0.31388368000000005" sigma="0.28419669108676826" />
   </LennardJonesForce>
+  <InitializationScript>
+EXPECTED_VERSION = "charmm36_2024"
+if hasattr(self, "_charmm_ff_version"):
+    if self._charmm_ff_version != EXPECTED_VERSION:
+        raise RuntimeError(f"CHARMM force field versions ({self._charmm_ff_version} and {EXPECTED_VERSION}) incompatible")
+else:
+    self._charmm_ff_version = EXPECTED_VERSION
+  </InitializationScript>
 </ForceField>
\ No newline at end of file

wrappers/python/openmm/app/data/charmm36_2024/water.xml

@@ -491,4 +491,12 @@
     <NBFixPair class1="CAL" class2="OC2D2" epsilon="0.50208" sigma="0.28793846570295767" />
     <NBFixPair class1="CAL" class2="OG2D2" epsilon="0.50208" sigma="0.28793846570295767" />
   </LennardJonesForce>
+  <InitializationScript>
+EXPECTED_VERSION = "charmm36_2024"
+if hasattr(self, "_charmm_ff_version"):
+    if self._charmm_ff_version != EXPECTED_VERSION:
+        raise RuntimeError(f"CHARMM force field versions ({self._charmm_ff_version} and {EXPECTED_VERSION}) incompatible")
+else:
+    self._charmm_ff_version = EXPECTED_VERSION
+  </InitializationScript>
 </ForceField>
\ No newline at end of file

wrappers/python/tests/TestForceField.py

@@ -1391,6 +1391,9 @@ END"""))
         """Tests that the CHARMM force fields are capable of parameterizing systems."""
 
         charmm_models = ("charmm36", "charmm36_2024")
+        water_models_3 = ("water", "spce", "tip3p-pme-b", "tip3p-pme-f")
+        water_models_4 = ("tip4p2005", "tip4pew")
+        water_models_5 = ("tip5p", "tip5pew")
 
         # Checks that the numbers of various types of terms in a system matches expected counts.
         def check_system(system, particle_count, site_count, constraint_count, bond_count, angle_count, cmap_count, exception_count, override_count, drude_count, screen_count):
@@ -1420,13 +1423,30 @@ END"""))
         pdb_peptide_4 = PDBFile("systems/test_charmm_peptide_4.pdb")
         pdb_peptide_5 = PDBFile("systems/test_charmm_peptide_5.pdb")
         for charmm_model in charmm_models:
-            for water_model in ("water", "spce", "tip3p-pme-b", "tip3p-pme-f"):
+            for water_model in water_models_3:
                 check_system(ForceField(f"{charmm_model}.xml", f"{charmm_model}/{water_model}.xml").createSystem(pdb_peptide_3.topology), 1136, 0, 984, 234, 249, 8, 1727, 353, 0, 0)
-            for water_model in ("tip4p2005", "tip4pew"):
+            for water_model in water_models_4:
                 check_system(ForceField(f"{charmm_model}.xml", f"{charmm_model}/{water_model}.xml").createSystem(pdb_peptide_4.topology), 1464, 328, 984, 234, 249, 8, 2711, 353, 0, 0)
-            for water_model in ("tip5p", "tip5pew"):
+            for water_model in water_models_5:
                 check_system(ForceField(f"{charmm_model}.xml", f"{charmm_model}/{water_model}.xml").createSystem(pdb_peptide_5.topology), 1792, 656, 984, 234, 249, 8, 4023, 353, 0, 0)
 
+    def test_CharmmVersionMismatchCheck(self):
+        """
+        Tests that CHARMM force fields cannot be loaded with the wrong water model versions.
+        """
+
+        charmm_models = ("charmm36", "charmm36_2024")
+        water_models = ("water", "spce", "tip3p-pme-b", "tip3p-pme-f", "tip4p2005", "tip4pew", "tip5p", "tip5pew")
+
+        for base_charmm_model in charmm_models:
+            for water_charmm_model in charmm_models:
+                if base_charmm_model != water_charmm_model:
+                    for water_model in water_models:
+                        with self.assertRaises(Exception):
+                            ForceField(f"{base_charmm_model}.xml", f"{water_charmm_model}/{water_model}.xml")
+                        with self.assertRaises(Exception):
+                            ForceField(f"{water_charmm_model}/{water_model}.xml", f"{base_charmm_model}.xml")
+
     def test_CharmmPolar(self):
         """Test the CHARMM polarizable force field."""
         pdb = PDBFile('systems/ala_ala_ala_drude.pdb')