-int tersoff_mult_post_2bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,u8 bc) {
-
- /* here we have to allow for the 3bp sums */
-
- t_tersoff_mult_params *params;
- t_tersoff_exchange *exchange;
-
- t_3dvec force,temp,*db_ij,*dist_ij;
- double db_ij_scale1,db_ij_scale2;
- double b_ij;
- double f_c,df_c,f_a,df_a;
- double chi,n,n_betan;
- double zeta;
-
- params=moldyn->pot2b_params;
- exchange=&(params->exchange);
-
- /* we do not run if f_c_ij was detected to be 0! */
- if(!(exchange->run2bp_post))
- return 0;
-
- db_ij=&(exchange->db_ij);
- f_c=exchange->f_c;
- df_c=exchange->df_c;
- f_a=exchange->f_a;
- df_a=exchange->df_a;
- n_betan=exchange->n_betan;
- n=*(exchange->n);
- chi=exchange->chi;
- dist_ij=&(exchange->dist_ij);
- zeta=exchange->zeta;
-
- db_ij_scale2=pow(zeta,n-1.0);
-printf("DEBUG: %.15f %.15f\n",zeta,db_ij_scale2);
- db_ij_scale1=db_ij_scale2*zeta;
- db_ij_scale2*=n_betan;
- db_ij_scale1=pow((1.0+n_betan*db_ij_scale1),-1.0/(2*n)-1);
- b_ij=chi*db_ij_scale1*(1.0+n_betan*db_ij_scale1);
- db_ij_scale1*=(-1.0*chi/(2*n));
-
- /* db_ij part */
- v3_scale(db_ij,db_ij,(db_ij_scale1*db_ij_scale2));
- v3_scale(db_ij,db_ij,f_a);
-
- /* df_a part */
- v3_scale(&temp,dist_ij,b_ij*df_a);
-
- /* db_ij + df_a part */
- v3_add(&force,&temp,db_ij);
- v3_scale(&force,&force,f_c);
-
- /* df_c part */
- v3_scale(&temp,dist_ij,f_a*b_ij*df_c);
-
- /* add energy of 3bp sum */
- moldyn->energy+=(0.5*f_c*b_ij*f_a);
-
- /* add force of 3bp calculation (all three parts) */
- v3_add(&(ai->f),&temp,&force);
-
- return 0;
-}
-
-/* tersoff 3 body part */
-
-int tersoff_mult_3bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,t_atom *ak,u8 bc) {
-
- t_tersoff_mult_params *params;
- t_tersoff_exchange *exchange;
- t_3dvec dist_ij,dist_ik,dist_jk;
- t_3dvec temp1,temp2;
- double R,S,s_r;
- double d_ij,d_ik,d_jk;
- double rxxryy,dxxdyy;
- double f_c,df_c,f_a,df_a;
- double f_c_ik,df_c_ik,arg;
- double n,c,d,h;
- double c2,d2,c2d2;
- double cos_theta,d_costheta1,d_costheta2;
- double h_cos,d2_h_cos2;
- double frac;
- double g;
- int num;
-
- params=moldyn->pot3b_params;
- exchange=&(params->exchange);
-
- if(!(exchange->run3bp))
- return 0;
-
- /*
- * calc of 3bp contribution of V_ij and dV_ij/ji/jk &
- * 2bp contribution of dV_jk
- *
- * for Vij and dV_ij we still need:
- * - b_ij, db_ij (zeta_ij)
- * - f_c_ik, df_c_ik, constants_i, cos_theta_ijk, d_costheta_ijk
- *
- * for dV_ji we still need:
- * - b_ji, db_ji (zeta_ji)
- * - f_c_jk, d_c_jk, constants_j, cos_theta_jik, d_costheta_jik
- *
- * for dV_jk we need:
- * - f_c_jk
- * - f_a_jk
- * - db_jk (zeta_jk)
- * - f_c_ji, df_c_ji, constants_j, cos_theta_jki, d_costheta_jki
- *
- */
-
- /*
- * get exchange data
- */
-
- /* dist_ij, d_ij - this is < S_ij ! */
- dist_ij=exchange->dist_ij;
- d_ij=exchange->d_ij;
-
- /* f_c_ij, df_c_ij (same for ji) */
- f_c=exchange->f_c;
- df_c=exchange->df_c;
-
- /*
- * calculate unknown values now ...
- */
-
- /* V_ij and dV_ij stuff (in b_ij there is f_c_ik) */
-
- /* dist_ik, d_ik */
- v3_sub(&dist_ik,&(ak->r),&(ai->r));
- if(bc) check_per_bound(moldyn,&dist_ik);
- d_ik=v3_norm(&dist_ik);
-
- /* ik constants */
- num=ai->bnum;
- if(num==ak->bnum) {
- R=params->R[num];
- S=params->S[num];
- }
- else {
- R=params->Rmixed;
- S=params->Smixed;
- }
-
- /* zeta_ij/dzeta_ij contribution only for d_ik < S */
- if(d_ik<S) {
-
- /* get constants_i from exchange data */
- n=*(exchange->n_i);
- c=*(exchange->c_i);
- d=*(exchange->d_i);
- h=*(exchange->h_i);
- c2=exchange->ci2;
- d2=exchange->di2;
- c2d2=exchange->ci2di2;
-
- /* cosine of theta_ijk by scalaproduct */
- rijrik=v3_scalar_product(&dist_ij,&dist_ik);
- dijdik=d_ij*d_ik;
- cos_theta=rijrik/dijdik;
-
- /* d_costheta */
- tmp=1.0/dijdik;
- d_costheta1=cos_theta/(d_ij*d_ij)-tmp;
- d_costheta2=cos_theta/(d_ik*d_ik)-tmp;
-
- /* some usefull values */
- h_cos=(h-cos_theta);
- d2_h_cos2=d2+(h_cos*h_cos);
- frac=c2/(d2_h_cos2);
-
- /* g(cos_theta) */
- g=1.0+c2d2-frac;
-
- /* d_costheta_ij and dg(cos_theta) - needed in any case! */
- v3_scale(&temp1,&dist_ij,d_costheta1);
- v3_scale(&temp2,&dist_ik,d_costheta2);
- v3_add(&temp1,&temp1,&temp2);
- v3_scale(&temp1,&temp1,-2.0*frac*h_cos/d2_h_cos2); /* dg */
-
- /* f_c_ik & df_c_ik + {d,}zeta contribution */
- if(d_ik<R) {
- /* {d,}f_c_ik */
- // => f_c_ik=1.0;
- // => df_c_ik=0.0; of course we do not set this!
-
- /* zeta_ij */
- exchange->zeta_ij+=g;
-
- /* dzeta_ij */
- v3_add(dzeta_ij,dzeta_ij,&temp1);
- }
- else {
- /* {d,}f_c_ik */
- s_r=S-R;
- arg=M_PI*(d_ik-R)/s_r;
- f_c_ik=0.5+0.5*cos(arg);
- df_c_ik=-0.5*sin(arg)*(M_PI/(s_r*d_ik));
-
- /* zeta_ij */
- exchange->zeta_ij+=f_c_ik*g;
-
- /* dzeta_ij */
- v3_scale(&temp1,&temp1,f_c_ik);
- v3_scale(&temp2,&dist_ik,g*df_c_ik);
- v3_add(dzeta_ij,&temp2,&temp1);
- }
- }
-
- /* dV_ji stuff (in b_ji there is f_c_jk) + dV_jk stuff! */
-
- /* dist_jk, d_jk */
- v3_sub(&dist_jk,&(ak->r),&(aj->r));
- if(bc) check_per_bound(moldyn,&dist_jk);
- d_jk=v3_norm(&dist_jk);
-
- /* jk constants */
- num=aj->bnum;
- if(num==ak->bnum) {
- R=params->R[num];
- S=params->S[num];
- }
- else {
- R=params->Rmixed;
- S=params->Smixed;
- }