--- trunk/src/primitives/Torsion.cpp	2010/06/17 14:48:02	1446
+++ trunk/src/primitives/Torsion.cpp	2013/06/16 15:15:42	1879
@@ -35,10 +35,14 @@
  *                                                                      
  * [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 {
@@ -47,7 +51,7 @@ namespace OpenMD {
 		   TorsionType *tt) :
     atom1_(atom1), atom2_(atom2), atom3_(atom3), atom4_(atom4), torsionType_(tt) { }
 
-  void Torsion::calcForce(RealType& angle) {
+  void Torsion::calcForce(RealType& angle, bool doParticlePot) {
 
     Vector3d pos1 = atom1_->getPos();
     Vector3d pos2 = atom2_->getPos();
@@ -98,10 +102,12 @@ namespace OpenMD {
     atom3_->addFrc(f3 - f2);
     atom4_->addFrc(-f3);
     
-    atom1_->addParticlePot(potential_);
-    atom2_->addParticlePot(potential_);
-    atom3_->addParticlePot(potential_);
-    atom4_->addParticlePot(potential_);
+    if (doParticlePot) {
+      atom1_->addParticlePot(potential_);
+      atom2_->addParticlePot(potential_);
+      atom3_->addParticlePot(potential_);
+      atom4_->addParticlePot(potential_);
+    }
     
     angle = acos(cos_phi) /M_PI * 180.0;    
   }