-/* create mixed terms from parameters and set them */
-int tersoff_mult_complete_params(t_tersoff_mult_params *p) {
-
- printf("[moldyn] tersoff parameter completion\n");
- p->Smixed=sqrt(p->S[0]*p->S[1]);
- p->Rmixed=sqrt(p->R[0]*p->R[1]);
- p->Amixed=sqrt(p->A[0]*p->A[1]);
- p->Bmixed=sqrt(p->B[0]*p->B[1]);
- p->lambda_m=0.5*(p->lambda[0]+p->lambda[1]);
- p->mu_m=0.5*(p->mu[0]+p->mu[1]);
-
- printf("[moldyn] tersoff mult parameter info:\n");
- printf(" S (A) | %f | %f | %f\n",p->S[0],p->S[1],p->Smixed);
- printf(" R (A) | %f | %f | %f\n",p->R[0],p->R[1],p->Rmixed);
- printf(" A (eV) | %f | %f | %f\n",p->A[0]/EV,p->A[1]/EV,p->Amixed/EV);
- printf(" B (eV) | %f | %f | %f\n",p->B[0]/EV,p->B[1]/EV,p->Bmixed/EV);
- printf(" lambda | %f | %f | %f\n",p->lambda[0],p->lambda[1],
- p->lambda_m);
- printf(" mu | %f | %f | %f\n",p->mu[0],p->mu[1],p->mu_m);
- printf(" beta | %.10f | %.10f\n",p->beta[0],p->beta[1]);
- printf(" n | %f | %f\n",p->n[0],p->n[1]);
- printf(" c | %f | %f\n",p->c[0],p->c[1]);
- printf(" d | %f | %f\n",p->d[0],p->d[1]);
- printf(" h | %f | %f\n",p->h[0],p->h[1]);
- printf(" chi | %f \n",p->chi);
-
- return 0;
-}
-
-/* tersoff 1 body part */
-int tersoff_mult_1bp(t_moldyn *moldyn,t_atom *ai) {
-
- int num;
- t_tersoff_mult_params *params;
- t_tersoff_exchange *exchange;
-
- num=ai->bnum;
- params=moldyn->pot1b_params;
- exchange=&(params->exchange);
-
- /*
- * simple: point constant parameters only depending on atom i to
- * their right values
- */
-
- exchange->beta_i=&(params->beta[num]);
- exchange->n_i=&(params->n[num]);
- exchange->c_i=&(params->c[num]);
- exchange->d_i=&(params->d[num]);
- exchange->h_i=&(params->h[num]);
-
- exchange->betaini=pow(*(exchange->beta_i),*(exchange->n_i));
- exchange->ci2=params->c[num]*params->c[num];
- exchange->di2=params->d[num]*params->d[num];
- exchange->ci2di2=exchange->ci2/exchange->di2;
-
- return 0;
-}
-
-/* tersoff 2 body part */
-int tersoff_mult_2bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,u8 bc) {
-
- t_tersoff_mult_params *params;
- t_tersoff_exchange *exchange;
- t_3dvec dist_ij,force;
- double d_ij;
- double A,B,R,S,lambda,mu;
- double f_r,df_r;
- double f_c,df_c;
- int num;
- double s_r;
- double arg;
-
- params=moldyn->pot2b_params;
- num=aj->bnum;
- exchange=&(params->exchange);
-
- /* clear 3bp and 2bp post run */
- exchange->run3bp=0;
- exchange->run2bp_post=0;
-
- /* reset S > r > R mark */
- exchange->d_ij_between_rs=0;
-
- /*
- * calc of 2bp contribution of V_ij and dV_ij/ji
- *
- * for Vij and dV_ij we need:
- * - f_c_ij, df_c_ij
- * - f_r_ij, df_r_ij
- *
- * for dV_ji we need:
- * - f_c_ji = f_c_ij, df_c_ji = df_c_ij
- * - f_r_ji = f_r_ij; df_r_ji = df_r_ij
- *
- */
-
- /* dist_ij, d_ij */
- v3_sub(&dist_ij,&(aj->r),&(ai->r));
- if(bc) check_per_bound(moldyn,&dist_ij);
- d_ij=v3_norm(&dist_ij);
-
- /* save for use in 3bp */
- exchange->d_ij=d_ij;
- exchange->dist_ij=dist_ij;
-
- /* constants */
- if(num==ai->bnum) {
- S=params->S[num];
- R=params->R[num];
- A=params->A[num];
- B=params->B[num];
- lambda=params->lambda[num];
- mu=params->mu[num];
- exchange->chi=1.0;
- }
- else {
- S=params->Smixed;
- R=params->Rmixed;
- A=params->Amixed;
- B=params->Bmixed;
- lambda=params->lambda_m;
- mu=params->mu_m;
- params->exchange.chi=params->chi;
- }
-
- /* if d_ij > S => no force & potential energy contribution */
- if(d_ij>S)
- return 0;
-
- /* more constants */
- exchange->beta_j=&(params->beta[num]);
- exchange->n_j=&(params->n[num]);
- exchange->c_j=&(params->c[num]);
- exchange->d_j=&(params->d[num]);
- exchange->h_j=&(params->h[num]);
- if(num==ai->bnum) {
- exchange->betajnj=exchange->betaini;
- exchange->cj2=exchange->ci2;
- exchange->dj2=exchange->di2;
- exchange->cj2dj2=exchange->ci2di2;
- }
- else {
- exchange->betajnj=pow(*(exchange->beta_j),*(exchange->n_j));
- exchange->cj2=params->c[num]*params->c[num];
- exchange->dj2=params->d[num]*params->d[num];
- exchange->cj2dj2=exchange->cj2/exchange->dj2;
- }
-
- /* f_r_ij = f_r_ji, df_r_ij = df_r_ji */
- f_r=A*exp(-lambda*d_ij);
- df_r=lambda*f_r/d_ij;
-
- /* f_a, df_a calc (again, same for ij and ji) | save for later use! */
- exchange->f_a=-B*exp(-mu*d_ij);
- exchange->df_a=mu*exchange->f_a/d_ij;
-
- /* f_c, df_c calc (again, same for ij and ji) */
- if(d_ij<R) {
- /* f_c = 1, df_c = 0 */
- f_c=1.0;
- df_c=0.0;
- /* two body contribution (ij, ji) */
- v3_scale(&force,&dist_ij,-df_r);
- }
- else {
- s_r=S-R;
- arg=M_PI*(d_ij-R)/s_r;
- f_c=0.5+0.5*cos(arg);
- df_c=-0.5*sin(arg)*(M_PI/(s_r*d_ij));
- /* two body contribution (ij, ji) */
- v3_scale(&force,&dist_ij,-df_c*f_r-df_r*f_c);
- /* tell 3bp that S > r > R */
- exchange->d_ij_between_rs=1;
- }
-
- /* add forces of 2bp (ij, ji) contribution
- * dVij = dVji and we sum up both: no 1/2) */
- v3_add(&(ai->f),&(ai->f),&force);
-
- /* energy 2bp contribution (ij, ji) is 0.5 f_r f_c ... */
- moldyn->energy+=(0.5*f_r*f_c);
-
- /* save for use in 3bp */
- exchange->f_c=f_c;
- exchange->df_c=df_c;
-
- /* enable the run of 3bp function and 2bp post processing */
- exchange->run3bp=1;
- exchange->run2bp_post=1;
-
- /* reset 3bp sums */
- exchange->zeta_ij=0.0;
- exchange->zeta_ji=0.0;
- v3_zero(&(exchange->dzeta_ij));
- v3_zero(&(exchange->dzeta_ji));
-
- return 0;
-}
-
-/* tersoff 2 body post part */
-
-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
- *
- * that is:
- * - zeta_ij, dzeta_ij
- * - zeta_ji, dzeta_ji
- *
- * to compute the 3bp contribution to:
- * - Vij, dVij
- * - dVji
- *
- */
-
- t_tersoff_mult_params *params;
- t_tersoff_exchange *exchange;
-
- t_3dvec force,temp;
- t_3dvec *dist_ij;
- double b,db,tmp;
- double f_c,df_c,f_a,df_a;
- double chi,ni,betaini,nj,betajnj;
- 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;
-
- f_c=exchange->f_c;
- df_c=exchange->df_c;
- f_a=exchange->f_a;
- df_a=exchange->df_a;
- betaini=exchange->betaini;
- betajnj=exchange->betajnj;
- ni=*(exchange->n_i);
- nj=*(exchange->n_j);
- chi=exchange->chi;
- dist_ij=&(exchange->dist_ij);
-
- /* Vij and dVij */
- zeta=exchange->zeta_ij;
- if(zeta==0.0) {
- moldyn->debug++; /* just for debugging ... */
- db=0.0;
- b=chi;
- v3_scale(&force,dist_ij,df_a*b*f_c);
- }
- else {
- tmp=betaini*pow(zeta,ni-1.0); /* beta^n * zeta^n-1 */
- b=(1+zeta*tmp); /* 1 + beta^n zeta^n */
- db=chi*pow(b,-1.0/(2*ni)-1); /* x(...)^(-1/2n - 1) */
- b=db*b; /* b_ij */
- db*=-0.5*tmp; /* db_ij */
- v3_scale(&force,&(exchange->dzeta_ij),f_a*db);
- v3_scale(&temp,dist_ij,df_a*b);
- v3_add(&force,&force,&temp);
- v3_scale(&force,&force,f_c);
- }
- v3_scale(&temp,dist_ij,df_c*b*f_a);
- v3_add(&force,&force,&temp);
- v3_scale(&force,&force,-0.5);
-
- /* add force */
- v3_add(&(ai->f),&(ai->f),&force);
-
- /* add energy of 3bp sum */
- moldyn->energy+=(0.5*f_c*b*f_a);
-
- /* dVji */
- zeta=exchange->zeta_ji;
- if(zeta==0.0) {
- moldyn->debug++;
- b=chi;
- v3_scale(&force,dist_ij,df_a*b*f_c);
- }
- else {
- tmp=betajnj*pow(zeta,nj-1.0); /* beta^n * zeta^n-1 */
- b=(1+zeta*tmp); /* 1 + beta^n zeta^n */
- db=chi*pow(b,-1.0/(2*nj)-1); /* x(...)^(-1/2n - 1) */
- b=db*b; /* b_ij */
- db*=-0.5*tmp; /* db_ij */
- v3_scale(&force,&(exchange->dzeta_ji),f_a*db);
- v3_scale(&temp,dist_ij,df_a*b);
- v3_add(&force,&force,&temp);
- v3_scale(&force,&force,f_c);
- }
- v3_scale(&temp,dist_ij,df_c*b*f_a);
- v3_add(&force,&force,&temp);
- v3_scale(&force,&force,-0.5);