--- branches/development/src/nonbonded/LJ.cpp	2011/07/08 20:25:32	1587
+++ branches/development/src/nonbonded/LJ.cpp	2011/09/14 21:15:17	1629
@@ -284,7 +284,7 @@ namespace OpenMD {
                                                                 myDerivC)*sigmai;      
 
       (*(idat.pot))[VANDERWAALS_FAMILY] += *(idat.sw) * pot_temp;
-      *(idat.f1) = *(idat.d) * dudr / *(idat.rij);
+      *(idat.f1) += *(idat.d) * dudr / *(idat.rij);
     }
     return;
   }