lennard jones force

[physik/posic.git] / moldyn.c

diff --git a/moldyn.c b/moldyn.c
index 82749b2..57ae62f 100644 (file)
--- a/moldyn.c
+++ b/moldyn.c
@@ -226,10 +226,16 @@ int force_lennard_jones(t_moldyn *moldyn) {
        t_3dvec distance;
        t_3dvec force;
        double d,h1,h2;
+       double eps,sig6,sig12;
 
        atom=moldyn->atom;      
        count=moldyn->count;
        params=moldyn->pot_params;
+       eps=params->epsilon;
+       sig6=params->sigma6;
+       sig12=params->sigma12;
+
+       for(i=0;i<count;i++) v3_zero(&(atom[i].f));
 
        for(i=0;i<count;i++) {
                for(j=0;j<i;j++) {
@@ -242,6 +248,13 @@ int force_lennard_jones(t_moldyn *moldyn) {
                                h2=d*d;                         /* 1/r^8 */
                                h1*=d;                          /* 1/r^6 */
                                h1*=h2;                         /* 1/r^14 */
+                               h1*=sig12;
+                               h2*=sig6;
+                               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);
                        }
                }
        }