--- trunk/src/primitives/GhostBend.cpp	2008/01/23 16:38:22	1211
+++ branches/development/src/primitives/GhostBend.cpp	2010/07/09 23:08:25	1465
@@ -6,19 +6,10 @@
  * redistribute this software in source and binary code form, provided
  * that the following conditions are met:
  *
- * 1. Acknowledgement of the program authors must be made in any
- *    publication of scientific results based in part on use of the
- *    program.  An acceptable form of acknowledgement is citation of
- *    the article in which the program was described (Matthew
- *    A. Meineke, Charles F. Vardeman II, Teng Lin, Christopher
- *    J. Fennell and J. Daniel Gezelter, "OOPSE: An Object-Oriented
- *    Parallel Simulation Engine for Molecular Dynamics,"
- *    J. Comput. Chem. 26, pp. 252-271 (2005))
- *
- * 2. Redistributions of source code must retain the above copyright
+ * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  *
- * 3. Redistributions in binary form must reproduce the above copyright
+ * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the
  *    distribution.
@@ -37,11 +28,20 @@
  * arising out of the use of or inability to use software, even if the
  * University of Notre Dame has been advised of the possibility of
  * such damages.
+ *
+ * SUPPORT OPEN SCIENCE!  If you use OpenMD or its source code in your
+ * research, please cite the appropriate papers when you publish your
+ * work.  Good starting points are:
+ *                                                                      
+ * [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).                        
  */
  
 #include "primitives/GhostBend.hpp"
 #include "primitives/DirectionalAtom.hpp"
-namespace oopse {
+namespace OpenMD {
 
   /**@todo still a lot left to improve*/
   void GhostBend::calcForce(RealType& angle) {
@@ -49,19 +49,20 @@ namespace oopse {
     
     Vector3d pos1 = atom1_->getPos();
     Vector3d pos2 = ghostAtom->getPos();
+
+    Vector3d r21 = pos1 - pos2;   
+    RealType d21 = r21.length();
     
-    Vector3d r12 = pos1 - pos2;
-    RealType d12 = r12.length();
+    RealType d21inv = 1.0 / d21;
+   
+    // we need the transpose of A to get the lab fixed vector:
+    Vector3d r23 = ghostAtom->getA().transpose().getColumn(2);
+    RealType d23 = r23.length();
     
-    RealType d12inv = 1.0 / d12;
+    RealType d23inv = 1.0 / d23;
     
-    Vector3d r32 = ghostAtom->getElectroFrame().getColumn(2);
-    RealType d32 = r32.length();
-    
-    RealType d32inv = 1.0 / d32;
-    
-    RealType cosTheta = dot(r12, r32) / (d12 * d32);
-    
+    RealType cosTheta = dot(r21, r23) / (d21 * d23);
+
     //check roundoff     
     if (cosTheta > 1.0) {
       cosTheta = 1.0;
@@ -70,29 +71,35 @@ namespace oopse {
     }
     
     RealType theta = acos(cosTheta);
+
+    RealType dVdTheta;
     
-    RealType firstDerivative;
+    bendType_->calcForce(theta, potential_, dVdTheta);
     
-    bendType_->calcForce(theta, firstDerivative, potential_);
-    
     RealType sinTheta = sqrt(1.0 - cosTheta * cosTheta);
     
-    if (fabs(sinTheta) < 1.0E-12) {
-      sinTheta = 1.0E-12;
+    if (fabs(sinTheta) < 1.0E-6) {
+      sinTheta = 1.0E-6;
     }
     
-    RealType commonFactor1 = -firstDerivative / sinTheta * d12inv;
-    RealType commonFactor2 = -firstDerivative / sinTheta * d32inv;
+    RealType commonFactor1 = dVdTheta / sinTheta * d21inv;
+    RealType commonFactor2 = dVdTheta / sinTheta * d23inv;
     
-    Vector3d force1 = commonFactor1*(r12*(d12inv*cosTheta) - r32*d32inv);
-    Vector3d force3 = commonFactor2*(r32*(d32inv*cosTheta) - r12*d12inv);
+    Vector3d force1 = commonFactor1 * (r23 * d23inv - r21*d21inv*cosTheta);
+    Vector3d force3 = commonFactor2 * (r21 * d21inv - r23*d23inv*cosTheta);
+
+    // Total force in current bend is zero
+
     atom1_->addFrc(force1);
     ghostAtom->addFrc(-force1);
-    /**@todo test correctness */
-    ghostAtom->addTrq(cross(r32, force3) );
-    
+
+    ghostAtom->addTrq( cross(r23, force3) );    
+
+    atom1_->addParticlePot(potential_);
+    ghostAtom->addParticlePot(potential_);
+
     angle = theta /M_PI * 180.0;
-    
+   
   }  
-} //end namespace oopse
+} //end namespace OpenMD