--- trunk/src/primitives/Inversion.cpp	2008/07/04 20:54:29	1275
+++ trunk/src/primitives/Inversion.cpp	2008/10/21 18:23:31	1309
@@ -60,39 +60,39 @@ namespace oopse {
     Vector3d pos3 = atom1_->getPos();
     Vector3d pos4 = atom4_->getPos();
 
-    Vector3d r21 = pos1 - pos2;
-    Vector3d r32 = pos2 - pos3;
+    Vector3d r31 = pos1 - pos3;
+    Vector3d r23 = pos3 - pos2;
     Vector3d r43 = pos3 - pos4;
 
     //  Calculate the cross products and distances
-    Vector3d A = cross(r21, r32);
+    Vector3d A = cross(r31, r43);
     RealType rA = A.length();
-    Vector3d B = cross(r32, r43);
+    Vector3d B = cross(r43, r23);
     RealType rB = B.length();
-    Vector3d C = cross(r32, A);
-    RealType rC = C.length();
+    //Vector3d C = cross(r23, A);
+    //RealType rC = C.length();
 
     A.normalize();
     B.normalize();
-    C.normalize();
+    //C.normalize();
     
     //  Calculate the sin and cos
     RealType cos_phi = dot(A, B) ;
     if (cos_phi > 1.0) cos_phi = 1.0;
-    if (cos_phi < -1.0) cos_phi = -1.0; 
+    if (cos_phi < -1.0) cos_phi = -1.0;
 
     RealType dVdcosPhi;
     inversionType_->calcForce(cos_phi, potential_, dVdcosPhi);
-    Vector3d f1;
-    Vector3d f2;
-    Vector3d f3;
+    Vector3d f1 ;
+    Vector3d f2 ;
+    Vector3d f3 ;
 
     Vector3d dcosdA = (cos_phi * A - B) /rA;
     Vector3d dcosdB = (cos_phi * B - A) /rB;
 
-    f1 = dVdcosPhi * cross(r32, dcosdA);
-    f2 = dVdcosPhi * ( cross(r43, dcosdB) - cross(r21, dcosdA));
-    f3 = dVdcosPhi * cross(dcosdB, r32);
+    f1 = dVdcosPhi * cross(r43, dcosdA);
+    f2 = dVdcosPhi * ( cross(r23, dcosdB) - cross(r31, dcosdA));
+    f3 = dVdcosPhi * cross(dcosdB, r43);
 
     // In OOPSE's version of an improper torsion, the central atom
     // comes first.  However, to get the planarity in a typical cosine
@@ -104,10 +104,16 @@ namespace oopse {
 
     // Confusing enough?  Good.
 
-    atom3_->addFrc(f1);
-    atom1_->addFrc(f2 - f1);
-    atom2_->addFrc(f3 - f2);
-    atom4_->addFrc(-f3);
+    atom2_->addFrc(f1);
+    atom1_->addFrc(f2 - f1 + f3);
+    atom4_->addFrc(-f2);
+    atom3_->addFrc(-f3);
+
+    atom1_->addParticlePot(potential_);
+    atom2_->addParticlePot(potential_);
+    atom3_->addParticlePot(potential_);
+    atom4_->addParticlePot(potential_);
+
     angle = acos(cos_phi) /M_PI * 180.0;
   }