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1   // ******************************************************************************
2   //
3   // Title:       Force Field X.
4   // Description: Force Field X - Software for Molecular Biophysics.
5   // Copyright:   Copyright (c) Michael J. Schnieders 2001-2025.
6   //
7   // This file is part of Force Field X.
8   //
9   // Force Field X is free software; you can redistribute it and/or modify it
10  // under the terms of the GNU General Public License version 3 as published by
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15  // FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
16  // details.
17  //
18  // You should have received a copy of the GNU General Public License along with
19  // Force Field X; if not, write to the Free Software Foundation, Inc., 59 Temple
20  // Place, Suite 330, Boston, MA 02111-1307 USA
21  //
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23  // combined work based on this library. Thus, the terms and conditions of the
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38  package ffx.potential.openmm;
39  
40  import ffx.openmm.Force;
41  import ffx.openmm.amoeba.GeneralizedKirkwoodForce;
42  import ffx.potential.bonded.Atom;
43  import ffx.potential.nonbonded.GeneralizedKirkwood;
44  import ffx.potential.parameters.ForceField;
45  import ffx.potential.parameters.MultipoleType;
46  
47  import java.util.logging.Level;
48  import java.util.logging.Logger;
49  
50  import static edu.uiowa.jopenmm.OpenMMAmoebaLibrary.OpenMM_AngstromsPerNm;
51  import static edu.uiowa.jopenmm.OpenMMAmoebaLibrary.OpenMM_KJPerKcal;
52  import static edu.uiowa.jopenmm.OpenMMAmoebaLibrary.OpenMM_NmPerAngstrom;
53  import static edu.uiowa.jopenmm.OpenMMLibrary.OpenMM_Boolean.OpenMM_False;
54  import static edu.uiowa.jopenmm.OpenMMLibrary.OpenMM_Boolean.OpenMM_True;
55  import static java.lang.String.format;
56  
57  public class AmoebaGeneralizedKirkwoodForce extends GeneralizedKirkwoodForce {
58  
59    private static final Logger logger = Logger.getLogger(AmoebaGeneralizedKirkwoodForce.class.getName());
60  
61    public AmoebaGeneralizedKirkwoodForce(OpenMMEnergy openMMEnergy) {
62      GeneralizedKirkwood gk = openMMEnergy.getGK();
63      if (gk == null) {
64        destroy();
65        return;
66      }
67  
68      setSolventDielectric(gk.getSolventPermittivity());
69      double soluteDielectric = gk.getSolutePermittivity();
70      if (soluteDielectric != 1.0) {
71        logger.severe(" Solute dielectric is not 1.0, which is not supported by OpenMM.");
72      }
73      setSoluteDielectric(1.0);
74      setDielectricOffset(gk.getDescreenOffset() * OpenMM_NmPerAngstrom);
75  
76  
77      boolean usePerfectRadii = gk.getUsePerfectRadii();
78      double perfectRadiiScale = 1.0;
79      if (usePerfectRadii) {
80        // No descreening when using perfect radii (OpenMM will just load the base radii).
81        perfectRadiiScale = 0.0;
82      }
83  
84      // Turn on tanh rescaling only when not using perfect radii.
85      int tanhRescale = 0;
86      if (gk.getTanhCorrection() && !usePerfectRadii) {
87        tanhRescale = 1;
88      }
89      double[] betas = gk.getTanhBetas();
90      setTanhRescaling(tanhRescale);
91      setTanhParameters(betas[0], betas[1], betas[2]);
92  
93      double[] baseRadius = gk.getBaseRadii();
94      if (usePerfectRadii) {
95        baseRadius = gk.getPerfectRadii();
96      }
97  
98      double[] overlapScale = gk.getOverlapScale();
99      double[] descreenRadius = gk.getDescreenRadii();
100     double[] neckFactor = gk.getNeckScale();
101 
102     if (!usePerfectRadii && logger.isLoggable(Level.FINE)) {
103       logger.fine("   GK Base Radii  Descreen Radius  Overlap Scale  Overlap");
104     }
105 
106     Atom[] atoms = openMMEnergy.getMolecularAssembly().getAtomArray();
107     int nAtoms = atoms.length;
108     for (int i = 0; i < nAtoms; i++) {
109       MultipoleType multipoleType = atoms[i].getMultipoleType();
110       double base = baseRadius[i] * OpenMM_NmPerAngstrom;
111       double descreen = descreenRadius[i] * OpenMM_NmPerAngstrom * perfectRadiiScale;
112       double overlap = overlapScale[i] * perfectRadiiScale;
113       double neck = neckFactor[i] * perfectRadiiScale;
114       addParticle_1(multipoleType.charge, base, overlap, descreen, neck);
115       if (!usePerfectRadii && logger.isLoggable(Level.FINE)) {
116         logger.fine(format("   %s %8.6f %8.6f %5.3f", atoms[i].toString(), baseRadius[i], descreenRadius[i], overlapScale[i]));
117       }
118     }
119 
120     setProbeRadius(gk.getProbeRadius() * OpenMM_NmPerAngstrom);
121 
122     GeneralizedKirkwood.NonPolarModel nonpolar = gk.getNonPolarModel();
123     switch (nonpolar) {
124       case BORN_CAV_DISP, BORN_SOLV -> {
125         // Configure a Born Radii based surface area term.
126         double surfaceTension = gk.getSurfaceTension() * OpenMM_KJPerKcal * OpenMM_AngstromsPerNm * OpenMM_AngstromsPerNm;
127         setIncludeCavityTerm(OpenMM_True);
128         setSurfaceAreaFactor(-surfaceTension);
129       }
130       // Other models do not use a Born Radii based surface area term.
131       default -> setIncludeCavityTerm(OpenMM_False);
132     }
133 
134     ForceField forceField = openMMEnergy.getMolecularAssembly().getForceField();
135     int forceGroup = forceField.getInteger("GK_FORCE_GROUP", 1);
136     setForceGroup(forceGroup);
137     logger.log(Level.INFO, format("  Generalized Kirkwood force \t\t%d", forceGroup));
138   }
139 
140   /**
141    * Convenience method to construct an AMOEBA Generalized Kirkwood Force.
142    *
143    * @param openMMEnergy The OpenMM Energy instance that contains the GK information.
144    * @return An AMOEBA GK Force, or null if there are no GK interactions.
145    */
146   public static Force constructForce(OpenMMEnergy openMMEnergy) {
147     GeneralizedKirkwood gk = openMMEnergy.getGK();
148     if (gk == null) {
149       return null;
150     }
151     return new AmoebaGeneralizedKirkwoodForce(openMMEnergy);
152   }
153 
154 
155   /**
156    * Update the force.
157    *
158    * @param atoms        The atoms to update.
159    * @param openMMEnergy The OpenMM energy.
160    */
161   public void updateForce(Atom[] atoms, OpenMMEnergy openMMEnergy) {
162     GeneralizedKirkwood gk = openMMEnergy.getGK();
163     if (gk == null || pointer == null) {
164       return;
165     }
166 
167     // Update the GK solute parameters.
168     int nAtoms = openMMEnergy.getMolecularAssembly().getAtomArray().length;
169     for (int i = 0; i < nAtoms; i++) {
170       gk.udpateSoluteParameters(i);
171     }
172 
173     boolean usePerfectRadii = gk.getUsePerfectRadii();
174     double perfectRadiiScale = 1.0;
175     if (usePerfectRadii) {
176       // No descreening when using perfect radii (OpenMM will just load the base radii).
177       perfectRadiiScale = 0.0;
178     }
179 
180     double[] baseRadii = gk.getBaseRadii();
181     if (usePerfectRadii) {
182       baseRadii = gk.getPerfectRadii();
183     }
184     double[] overlapScale = gk.getOverlapScale();
185     double[] descreenRadius = gk.getDescreenRadii();
186     double[] neckFactors = gk.getNeckScale();
187 
188     boolean nea = gk.getNativeEnvironmentApproximation();
189     double lambdaElec = openMMEnergy.getPmeNode().getAlchemicalParameters().permLambda;
190 
191     for (Atom atom : atoms) {
192       int index = atom.getXyzIndex() - 1;
193       double chargeUseFactor = 1.0;
194       if (!atom.getUse() || !atom.getElectrostatics()) {
195         chargeUseFactor = 0.0;
196       }
197 
198       double lambdaScale = lambdaElec;
199       if (!atom.applyLambda()) {
200         lambdaScale = 1.0;
201       }
202 
203       double baseSize = baseRadii[index] * OpenMM_NmPerAngstrom;
204       double descreenSize = descreenRadius[index] * OpenMM_NmPerAngstrom * perfectRadiiScale;
205 
206       chargeUseFactor *= lambdaScale;
207       double overlapScaleUseFactor = nea ? 1.0 : chargeUseFactor;
208       overlapScaleUseFactor = overlapScaleUseFactor * perfectRadiiScale;
209       double overlap = overlapScale[index] * overlapScaleUseFactor;
210       double neckFactor = neckFactors[index] * overlapScaleUseFactor;
211 
212       MultipoleType multipoleType = atom.getMultipoleType();
213       setParticleParameters_1(index, multipoleType.charge * chargeUseFactor, baseSize, overlap, descreenSize, neckFactor);
214     }
215 
216     // OpenMM Bug: Surface Area is not Updated by "updateParametersInContext"
217     GeneralizedKirkwood.NonPolarModel nonpolar = gk.getNonPolarModel();
218     switch (nonpolar) {
219       case BORN_CAV_DISP, BORN_SOLV -> {
220         // Configure a Born Radii based surface area term.
221         double surfaceTension = gk.getSurfaceTension() * OpenMM_KJPerKcal * OpenMM_AngstromsPerNm * OpenMM_AngstromsPerNm;
222         setSurfaceAreaFactor(-surfaceTension);
223       }
224     }
225 
226     updateParametersInContext(openMMEnergy.getContext());
227   }
228 }