-
-/*
- * example potentials
- */
-
-/* harmonic oscillator potential and force */
-
-int harmonic_oscillator(t_moldyn *moldyn,t_atom *ai,t_atom *aj,u8 bc) {
-
- t_ho_params *params;
- t_3dvec force,distance;
- double d,f;
- double sc,equi_dist;
-
- params=moldyn->pot2b_params;
- sc=params->spring_constant;
- equi_dist=params->equilibrium_distance;
-
- if(ai<aj) return 0;
-
- v3_sub(&distance,&(aj->r),&(ai->r));
-
- if(bc) check_per_bound(moldyn,&distance);
- d=v3_norm(&distance);
- if(d<=moldyn->cutoff) {
- moldyn->energy+=(0.5*sc*(d-equi_dist)*(d-equi_dist));
- /* f = -grad E; grad r_ij = -1 1/r_ij distance */
- f=sc*(1.0-equi_dist/d);
- v3_scale(&force,&distance,f);
- v3_add(&(ai->f),&(ai->f),&force);
- virial_calc(ai,&force,&distance);
- virial_calc(aj,&force,&distance); /* f and d signe switched */
- v3_scale(&force,&distance,-f);
- v3_add(&(aj->f),&(aj->f),&force);
- }
-
- return 0;
-}
-