X-Git-Url: https://hackdaworld.org/gitweb/?a=blobdiff_plain;f=moldyn.c;h=db575e9059ac2f88ebad208af55fb28e3053624c;hb=8358faac044f73487d64f5ba46690dd84367e532;hp=0fd1aca88d3b7243ee58cbe2d219cf0e4e2190f9;hpb=512390ceb93a2dd630943165b35bba683e0ffcfc;p=physik%2Fposic.git

diff --git a/moldyn.c b/moldyn.c
index 0fd1aca..db575e9 100644
--- a/moldyn.c
+++ b/moldyn.c
@@ -547,7 +547,7 @@ double potential_lennard_jones(t_moldyn *moldyn) {
 	params=moldyn->pot_params;
 	atom=moldyn->atom;
 	count=moldyn->count;
-	eps=params->epsilon;
+	eps=params->epsilon4;
 	sig6=params->sigma6;
 	sig12=params->sigma12;
 
@@ -559,7 +559,7 @@ double potential_lennard_jones(t_moldyn *moldyn) {
 			help=d*d; 				/* 1/r^4 */
 			help*=d; 				/* 1/r^6 */
 			d=help*help; 				/* 1/r^12 */
-			u+=eps*(sig12*d-sig6*help);
+			u+=eps*(sig6*help-sig12*d);
 		}
 	}
 	
@@ -579,7 +579,7 @@ int force_lennard_jones(t_moldyn *moldyn) {
 	atom=moldyn->atom;	
 	count=moldyn->count;
 	params=moldyn->pot_params;
-	eps=params->epsilon;
+	eps=params->epsilon4;
 	sig6=params->sigma6;
 	sig12=params->sigma12;
 
@@ -598,11 +598,13 @@ int force_lennard_jones(t_moldyn *moldyn) {
 				h1*=h2;				/* 1/r^14 */
 				h1*=sig12;
 				h2*=sig6;
-				d=12.0*h1-6.0*h2;
+				/* actually there would be a '-',	*
+				 * but f=-d/dr potential		*/
+				d=-12.0*h1+6.0*h2;
 				d*=eps;
 				v3_scale(&force,&distance,d);
-				v3_add(&(atom[j].f),&(atom[j].f),&force);
-				v3_sub(&(atom[i].f),&(atom[i].f),&force);
+				v3_add(&(atom[i].f),&(atom[i].f),&force);
+				v3_sub(&(atom[j].f),&(atom[j].f),&force);
 			}
 		}
 	}