--- trunk/src/primitives/Torsion.cpp	2010/06/17 14:48:02	1446
+++ trunk/src/primitives/Torsion.cpp	2013/12/05 18:19:26	1953
@@ -35,24 +35,34 @@
  *                                                                      
  * [1]  Meineke, et al., J. Comp. Chem. 26, 252-271 (2005).             
  * [2]  Fennell & Gezelter, J. Chem. Phys. 124, 234104 (2006).          
- * [3]  Sun, Lin & Gezelter, J. Chem. Phys. 128, 24107 (2008).          
- * [4]  Vardeman & Gezelter, in progress (2009).                        
+ * [3]  Sun, Lin & Gezelter, J. Chem. Phys. 128, 234107 (2008).          
+ * [4]  Kuang & Gezelter,  J. Chem. Phys. 133, 164101 (2010).
+ * [5]  Vardeman, Stocker & Gezelter, J. Chem. Theory Comput. 7, 834 (2011).
  */
  
+#include "config.h"
+#include <cmath>
+
 #include "primitives/Torsion.hpp"
 
 namespace OpenMD {
 
   Torsion::Torsion(Atom *atom1, Atom *atom2, Atom *atom3, Atom *atom4,
-		   TorsionType *tt) :
-    atom1_(atom1), atom2_(atom2), atom3_(atom3), atom4_(atom4), torsionType_(tt) { }
+		   TorsionType *tt) : ShortRangeInteraction(),
+                                      torsionType_(tt) {
+    atoms_.resize(4);
+    atoms_[0] = atom1;
+    atoms_[1] = atom2;
+    atoms_[2] = atom3;
+    atoms_[3] = atom4;
+  }
 
-  void Torsion::calcForce(RealType& angle) {
+  void Torsion::calcForce(RealType& angle, bool doParticlePot) {
 
-    Vector3d pos1 = atom1_->getPos();
-    Vector3d pos2 = atom2_->getPos();
-    Vector3d pos3 = atom3_->getPos();
-    Vector3d pos4 = atom4_->getPos();
+    Vector3d pos1 = atoms_[0]->getPos();
+    Vector3d pos2 = atoms_[1]->getPos();
+    Vector3d pos3 = atoms_[2]->getPos();
+    Vector3d pos4 = atoms_[3]->getPos();
 
     Vector3d r21 = pos1 - pos2;
     Vector3d r32 = pos2 - pos3;
@@ -93,15 +103,17 @@ namespace OpenMD {
     f2 = dVdcosPhi * ( cross(r43, dcosdB) - cross(r21, dcosdA));
     f3 = dVdcosPhi * cross(dcosdB, r32);
     
-    atom1_->addFrc(f1);
-    atom2_->addFrc(f2 - f1);
-    atom3_->addFrc(f3 - f2);
-    atom4_->addFrc(-f3);
+    atoms_[0]->addFrc(f1);
+    atoms_[1]->addFrc(f2 - f1);
+    atoms_[2]->addFrc(f3 - f2);
+    atoms_[3]->addFrc(-f3);
     
-    atom1_->addParticlePot(potential_);
-    atom2_->addParticlePot(potential_);
-    atom3_->addParticlePot(potential_);
-    atom4_->addParticlePot(potential_);
+    if (doParticlePot) {
+      atoms_[0]->addParticlePot(potential_);
+      atoms_[1]->addParticlePot(potential_);
+      atoms_[2]->addParticlePot(potential_);
+      atoms_[3]->addParticlePot(potential_);
+    }
     
     angle = acos(cos_phi) /M_PI * 180.0;    
   }