+int destroy_lattice(t_atom *atom) {
+
+ if(atom) free(atom);
+
+ return 0;
+}
+
+int thermal_init(t_moldyn *moldyn) {
+
+ /*
+ * - gaussian distribution of velocities
+ * - zero total momentum
+ * - velocity scaling (E = 3/2 N k T), E: kinetic energy
+ */
+
+ int i;
+ double v,sigma;
+ t_3dvec p_total,delta;
+ t_atom *atom;
+ t_random *random;
+
+ atom=moldyn->atom;
+ random=&(moldyn->random);
+
+ /* gaussian distribution of velocities */
+ v3_zero(&p_total);
+ for(i=0;i<moldyn->count;i++) {
+ sigma=sqrt(2.0*K_BOLTZMANN*moldyn->t/atom[i].mass);
+ /* x direction */
+ v=sigma*rand_get_gauss(random);
+ atom[i].v.x=v;
+ p_total.x+=atom[i].mass*v;
+ /* y direction */
+ v=sigma*rand_get_gauss(random);
+ atom[i].v.y=v;
+ p_total.y+=atom[i].mass*v;
+ /* z direction */
+ v=sigma*rand_get_gauss(random);
+ atom[i].v.z=v;
+ p_total.z+=atom[i].mass*v;
+ }
+
+ /* zero total momentum */
+ v3_scale(&p_total,&p_total,1.0/moldyn->count);
+ for(i=0;i<moldyn->count;i++) {
+ v3_scale(&delta,&p_total,1.0/atom[i].mass);
+ v3_sub(&(atom[i].v),&(atom[i].v),&delta);
+ }
+
+ /* velocity scaling */
+ scale_velocity(moldyn);
+
+ return 0;
+}
+
+int scale_velocity(t_moldyn *moldyn) {
+
+ int i;
+ double e,c;
+ t_atom *atom;
+
+ atom=moldyn->atom;
+
+ /*
+ * - velocity scaling (E = 3/2 N k T), E: kinetic energy
+ */
+ e=0.0;
+ for(i=0;i<moldyn->count;i++)
+ e+=0.5*atom[i].mass*v3_absolute_square(&(atom[i].v));
+ c=sqrt((2.0*e)/(3.0*moldyn->count*K_BOLTZMANN*moldyn->t));
+ for(i=0;i<moldyn->count;i++)
+ v3_scale(&(atom[i].v),&(atom[i].v),(1.0/c));
+
+ return 0;
+}
+
+double get_e_kin(t_atom *atom,int count) {
+
+ int i;
+ double e;
+
+ e=0.0;
+
+ for(i=0;i<count;i++) {
+ e+=0.5*atom[i].mass*v3_absolute_square(&(atom[i].v));
+ }
+
+ return e;
+}
+
+double get_e_pot(t_moldyn *moldyn) {
+
+ return moldyn->energy;
+}
+
+double get_total_energy(t_moldyn *moldyn) {
+
+ double e;
+
+ e=get_e_kin(moldyn->atom,moldyn->count);
+ e+=get_e_pot(moldyn);
+
+ return e;
+}
+
+t_3dvec get_total_p(t_atom *atom, int count) {
+
+ t_3dvec p,p_total;
+ int i;
+
+ v3_zero(&p_total);
+ for(i=0;i<count;i++) {
+ v3_scale(&p,&(atom[i].v),atom[i].mass);
+ v3_add(&p_total,&p_total,&p);
+ }
+
+ return p_total;
+}
+
+double estimate_time_step(t_moldyn *moldyn,double nn_dist,double t) {
+
+ double tau;
+
+ tau=0.05*nn_dist/(sqrt(3.0*K_BOLTZMANN*t/moldyn->atom[0].mass));
+ tau*=1.0E-9;
+ if(tau<moldyn->tau)
+ printf("[moldyn] warning: time step (%f > %.15f)\n",
+ moldyn->tau,tau);
+
+ return tau;
+}
+
+/*
+ * numerical tricks
+ */
+
+/* linked list / cell method */
+
+int link_cell_init(t_moldyn *moldyn) {
+
+ t_linkcell *lc;
+ int i;
+
+ lc=&(moldyn->lc);
+
+ /* list log fd */
+ lc->listfd=open("/dev/null",O_WRONLY);
+
+ /* partitioning the md cell */
+ lc->nx=moldyn->dim.x/moldyn->cutoff;
+ lc->x=moldyn->dim.x/lc->nx;
+ lc->ny=moldyn->dim.y/moldyn->cutoff;
+ lc->y=moldyn->dim.y/lc->ny;
+ lc->nz=moldyn->dim.z/moldyn->cutoff;
+ lc->z=moldyn->dim.z/lc->nz;
+
+ lc->cells=lc->nx*lc->ny*lc->nz;
+ lc->subcell=malloc(lc->cells*sizeof(t_list));
+
+ printf("initializing linked cells (%d)\n",lc->cells);
+
+ for(i=0;i<lc->cells;i++)
+ //list_init(&(lc->subcell[i]),1);
+ list_init(&(lc->subcell[i]));
+
+ link_cell_update(moldyn);
+
+ return 0;
+}
+
+int link_cell_update(t_moldyn *moldyn) {
+
+ int count,i,j,k;
+ int nx,ny,nz;
+ t_atom *atom;
+ t_linkcell *lc;
+
+ atom=moldyn->atom;
+ lc=&(moldyn->lc);
+
+ nx=lc->nx;
+ ny=lc->ny;
+ nz=lc->nz;
+
+ for(i=0;i<lc->cells;i++)
+ list_destroy(&(moldyn->lc.subcell[i]));
+
+ for(count=0;count<moldyn->count;count++) {
+ i=(atom[count].r.x+(moldyn->dim.x/2))/lc->x;
+ j=(atom[count].r.y+(moldyn->dim.y/2))/lc->y;
+ k=(atom[count].r.z+(moldyn->dim.z/2))/lc->z;
+ list_add_immediate_ptr(&(moldyn->lc.subcell[i+j*nx+k*nx*ny]),
+ &(atom[count]));
+ }
+
+ return 0;
+}
+
+int link_cell_neighbour_index(t_moldyn *moldyn,int i,int j,int k,t_list *cell) {
+
+ t_linkcell *lc;
+ int a;
+ int count1,count2;
+ int ci,cj,ck;
+ int nx,ny,nz;
+ int x,y,z;
+ unsigned char bx,by,bz;
+
+ lc=&(moldyn->lc);
+ nx=lc->nx;
+ ny=lc->ny;
+ nz=lc->nz;
+ count1=1;
+ count2=27;
+ a=nx*ny;
+
+
+ cell[0]=lc->subcell[i+j*nx+k*a];
+ for(ci=-1;ci<=1;ci++) {
+ bx=0;
+ x=i+ci;
+ if((x<0)||(x>=nx)) {
+ x=(x+nx)%nx;
+ bx=1;
+ }
+ for(cj=-1;cj<=1;cj++) {
+ by=0;
+ y=j+cj;
+ if((y<0)||(y>=ny)) {
+ y=(y+ny)%ny;
+ by=1;
+ }
+ for(ck=-1;ck<=1;ck++) {
+ bz=0;
+ z=k+ck;
+ if((z<0)||(z>=nz)) {
+ z=(z+nz)%nz;
+ bz=1;
+ }
+ if(!(ci|cj|ck)) continue;
+ if(bx|by|bz) {
+ cell[--count2]=lc->subcell[x+y*nx+z*a];
+ }
+ else {
+ cell[count1++]=lc->subcell[x+y*nx+z*a];
+ }
+ }
+ }
+ }
+
+ return count2;
+}
+
+int link_cell_shutdown(t_moldyn *moldyn) {
+
+ int i;
+ t_linkcell *lc;
+
+ lc=&(moldyn->lc);
+
+ for(i=0;i<lc->nx*lc->ny*lc->nz;i++)
+ list_shutdown(&(moldyn->lc.subcell[i]));
+
+ if(lc->listfd) close(lc->listfd);
+
+ return 0;
+}
+
+/*
+ *
+ * 'integration of newtons equation' - algorithms
+ *
+ */
+
+/* start the integration */
+
+int moldyn_integrate(t_moldyn *moldyn) {
+
+ int i;
+ unsigned int e,m,s,d,v;
+ t_3dvec p;
+
+ int fd;
+ char fb[128];
+
+ /* initialize linked cell method */
+ link_cell_init(moldyn);
+
+ /* logging & visualization */
+ e=moldyn->ewrite;
+ m=moldyn->mwrite;
+ s=moldyn->swrite;
+ d=moldyn->dwrite;
+ v=moldyn->vwrite;
+
+ if(!(moldyn->lvstat&MOLDYN_LVSTAT_INITIALIZED)) {
+ printf("[moldyn] warning, lv system not initialized\n");
+ return -1;
+ }
+
+ /* sqaure of some variables */
+ moldyn->tau_square=moldyn->tau*moldyn->tau;
+ moldyn->cutoff_square=moldyn->cutoff*moldyn->cutoff;
+
+ /* calculate initial forces */
+ moldyn->potential_force_function(moldyn);
+
+ for(i=0;i<moldyn->time_steps;i++) {
+
+ /* integration step */
+ moldyn->integrate(moldyn);
+
+ /* check for log & visualization */
+ if(e) {
+ if(!(i%e))
+ dprintf(moldyn->efd,
+ "%.15f %.45f\n",i*moldyn->tau,
+ get_total_energy(moldyn));
+ }
+ if(m) {
+ if(!(i%m)) {
+ p=get_total_p(moldyn->atom,moldyn->count);
+ dprintf(moldyn->mfd,
+ "%.15f %.45f\n",i*moldyn->tau,
+ v3_norm(&p));
+ }
+ }
+ if(s) {
+ if(!(i%s)) {
+ snprintf(fb,128,"%s-%f-%.15f.save",moldyn->sfb,
+ moldyn->t,i*moldyn->tau);
+ fd=open(fb,O_WRONLY|O_TRUNC|O_CREAT);
+ if(fd<0) perror("[moldyn] save fd open");
+ else {
+ write(fd,moldyn,sizeof(t_moldyn));
+ write(fd,moldyn->atom,
+ moldyn->count*sizeof(t_atom));
+ }
+ }
+ }
+ if(d) {
+ if(!(i%d))
+ write(moldyn->dfd,moldyn->atom,
+ moldyn->count*sizeof(t_atom));
+
+ }
+ if(v) {
+ if(!(i%v)) {
+ visual_atoms(moldyn->visual,i*moldyn->tau,
+ moldyn->atom,moldyn->count);
+ printf("\rsteps: %d",i);
+ fflush(stdout);
+ }
+ }
+ }
+
+ return 0;
+}
+
+/* velocity verlet */
+
+int velocity_verlet(t_moldyn *moldyn) {
+
+ int i,count;
+ double tau,tau_square;
+ t_3dvec delta;
+ t_atom *atom;
+
+ atom=moldyn->atom;
+ count=moldyn->count;
+ tau=moldyn->tau;
+ tau_square=moldyn->tau_square;
+
+ for(i=0;i<count;i++) {
+ /* new positions */
+ v3_scale(&delta,&(atom[i].v),tau);
+ v3_add(&(atom[i].r),&(atom[i].r),&delta);
+ v3_scale(&delta,&(atom[i].f),0.5*tau_square/atom[i].mass);
+ v3_add(&(atom[i].r),&(atom[i].r),&delta);
+ v3_per_bound(&(atom[i].r),&(moldyn->dim));
+
+ /* velocities */
+ v3_scale(&delta,&(atom[i].f),0.5*tau/atom[i].mass);
+ v3_add(&(atom[i].v),&(atom[i].v),&delta);
+ }
+
+ /* neighbour list update */
+printf("list update ...\n");
+ link_cell_update(moldyn);
+printf("done\n");
+
+ /* forces depending on chosen potential */
+printf("calc potential/force ...\n");
+ moldyn->potential_force_function(moldyn);
+printf("done\n");
+
+ for(i=0;i<count;i++) {
+ /* again velocities */
+ v3_scale(&delta,&(atom[i].f),0.5*tau/atom[i].mass);
+ v3_add(&(atom[i].v),&(atom[i].v),&delta);
+ }
+
+ return 0;
+}
+
+
+/*
+ *
+ * potentials & corresponding forces
+ *
+ */
+
+/* harmonic oscillator potential and force */
+
+int harmonic_oscillator(t_moldyn *moldyn) {
+
+ t_ho_params *params;
+ t_atom *atom,*btom;
+ t_linkcell *lc;
+ t_list *this,neighbour[27];
+ int i,j,c;
+ int count;
+ t_3dvec force,distance;
+ double d,u;
+ double sc,equi_dist;
+ int ni,nj,nk;
+
+ params=moldyn->pot_params;
+ atom=moldyn->atom;
+ lc=&(moldyn->lc);
+ sc=params->spring_constant;
+ equi_dist=params->equilibrium_distance;
+ count=moldyn->count;
+
+ /* reset energy counter */
+ u=0.0;
+
+ for(i=0;i<count;i++) {
+ /* reset force */
+ v3_zero(&(atom[i].f));
+
+ /* determine cell + neighbours */
+ ni=(atom[i].r.x+(moldyn->dim.x/2))/lc->x;
+ nj=(atom[i].r.y+(moldyn->dim.y/2))/lc->y;
+ nk=(atom[i].r.z+(moldyn->dim.z/2))/lc->z;
+ c=link_cell_neighbour_index(moldyn,ni,nj,nk,neighbour);
+
+ /*
+ * processing cell of atom i
+ * => no need to check for empty list (1 element at minimum)
+ */
+ this=&(neighbour[0]);
+ list_reset(this);
+ do {
+ btom=this->current->data;
+ if(btom==&(atom[i]))
+ continue;
+ v3_sub(&distance,&(atom[i].r),&(btom->r));
+ d=v3_norm(&distance);
+ if(d<=moldyn->cutoff) {
+ u+=(0.5*sc*(d-equi_dist)*(d-equi_dist));
+ v3_scale(&force,&distance,
+ -sc*(1.0-(equi_dist/d)));
+ v3_add(&(atom[i].f),&(atom[i].f),&force);
+ }
+ } while(list_next(this)!=L_NO_NEXT_ELEMENT);
+
+ /*
+ * direct neighbour cells
+ * => no boundary condition check necessary
+ */
+ for(j=1;j<c;j++) {
+ this=&(neighbour[j]);
+ list_reset(this); /* there might not be a single atom */
+ if(this->start!=NULL) {
+
+ do {
+ btom=this->current->data;
+ v3_sub(&distance,&(atom[i].r),&(btom->r));
+ d=v3_norm(&distance);
+ if(d<=moldyn->cutoff) {
+ u+=(0.5*sc*(d-equi_dist)*(d-equi_dist));
+ v3_scale(&force,&distance,
+ -sc*(1.0-(equi_dist/d)));
+ v3_add(&(atom[i].f),&(atom[i].f),
+ &force);
+ }
+ } while(list_next(this)!=L_NO_NEXT_ELEMENT);
+
+ }
+ }
+
+ /*
+ * indirect neighbour cells
+ * => check boundary conditions
+ */
+ for(j=c;j<27;j++) {
+ this=&(neighbour[j]);
+ list_reset(this); /* check boundary conditions */
+ if(this->start!=NULL) {
+
+ do {
+ btom=this->current->data;
+ v3_sub(&distance,&(atom[i].r),&(btom->r));
+ v3_per_bound(&distance,&(moldyn->dim));
+ d=v3_norm(&distance);
+ if(d<=moldyn->cutoff) {
+ u+=(0.5*sc*(d-equi_dist)*(d-equi_dist));
+ v3_scale(&force,&distance,
+ -sc*(1.0-(equi_dist/d)));
+ v3_add(&(atom[i].f),&(atom[i].f),
+ &force);
+ }
+ } while(list_next(this)!=L_NO_NEXT_ELEMENT);
+
+ }
+ }
+ }
+
+ moldyn->energy=0.5*u;
+
+ return 0;
+}
+
+/* lennard jones potential & force for one sort of atoms */
+
+int lennard_jones(t_moldyn *moldyn) {
+
+ t_lj_params *params;
+ t_atom *atom,*btom;
+ t_linkcell *lc;
+ t_list *this,neighbour[27];
+ int i,j,c;
+ int count;
+ t_3dvec force,distance;
+ double d,h1,h2,u;
+ double eps,sig6,sig12;
+ int ni,nj,nk;
+
+ params=moldyn->pot_params;
+ atom=moldyn->atom;
+ lc=&(moldyn->lc);
+ count=moldyn->count;
+ eps=params->epsilon4;
+ sig6=params->sigma6;
+ sig12=params->sigma12;
+
+ /* reset energy counter */
+ u=0.0;
+
+ for(i=0;i<count;i++) {
+ /* reset force */
+ v3_zero(&(atom[i].f));
+
+ /* determine cell + neighbours */
+ ni=(atom[i].r.x+(moldyn->dim.x/2))/lc->x;
+ nj=(atom[i].r.y+(moldyn->dim.y/2))/lc->y;
+ nk=(atom[i].r.z+(moldyn->dim.z/2))/lc->z;
+ c=link_cell_neighbour_index(moldyn,ni,nj,nk,neighbour);
+
+ /* processing cell of atom i */
+ this=&(neighbour[0]);
+ list_reset(this); /* list has 1 element at minimum */
+ do {
+ btom=this->current->data;
+ if(btom==&(atom[i]))
+ continue;
+ v3_sub(&distance,&(atom[i].r),&(btom->r));
+ d=v3_absolute_square(&distance); /* 1/r^2 */
+ if(d<=moldyn->cutoff_square) {
+ d=1.0/d; /* 1/r^2 */
+ h2=d*d; /* 1/r^4 */
+ h2*=d; /* 1/r^6 */
+ h1=h2*h2; /* 1/r^12 */
+ u+=eps*(sig12*h1-sig6*h2);
+ h2*=d; /* 1/r^8 */
+ h1*=d; /* 1/r^14 */
+ h2*=6*sig6;
+ h1*=12*sig12;
+ d=+h1-h2;
+ d*=eps;
+ v3_scale(&force,&distance,d);
+ v3_add(&(atom[i].f),&(atom[i].f),&force);
+ }
+ } while(list_next(this)!=L_NO_NEXT_ELEMENT);
+
+ /* neighbours not doing boundary condition overflow */
+ for(j=1;j<c;j++) {
+ this=&(neighbour[j]);
+ list_reset(this); /* there might not be a single atom */
+ if(this->start!=NULL) {
+
+ do {
+ btom=this->current->data;
+ v3_sub(&distance,&(atom[i].r),&(btom->r));
+ d=v3_absolute_square(&distance); /* r^2 */
+ if(d<=moldyn->cutoff_square) {
+ d=1.0/d; /* 1/r^2 */
+ h2=d*d; /* 1/r^4 */
+ h2*=d; /* 1/r^6 */
+ h1=h2*h2; /* 1/r^12 */
+ u+=eps*(sig12*h1-sig6*h2);
+ h2*=d; /* 1/r^8 */
+ h1*=d; /* 1/r^14 */
+ h2*=6*sig6;
+ h1*=12*sig12;
+ d=+h1-h2;
+ d*=eps;
+ v3_scale(&force,&distance,d);
+ v3_add(&(atom[i].f),&(atom[i].f),
+ &force);
+ }
+ } while(list_next(this)!=L_NO_NEXT_ELEMENT);
+
+ }
+ }
+
+ /* neighbours due to boundary conditions */
+ for(j=c;j<27;j++) {
+ this=&(neighbour[j]);
+ list_reset(this); /* check boundary conditions */
+ if(this->start!=NULL) {
+
+ do {
+ btom=this->current->data;
+ v3_sub(&distance,&(atom[i].r),&(btom->r));
+ v3_per_bound(&distance,&(moldyn->dim));
+ d=v3_absolute_square(&distance); /* r^2 */
+ if(d<=moldyn->cutoff_square) {
+ d=1.0/d; /* 1/r^2 */
+ h2=d*d; /* 1/r^4 */
+ h2*=d; /* 1/r^6 */
+ h1=h2*h2; /* 1/r^12 */
+ u+=eps*(sig12*h1-sig6*h2);
+ h2*=d; /* 1/r^8 */
+ h1*=d; /* 1/r^14 */
+ h2*=6*sig6;
+ h1*=12*sig12;
+ d=+h1-h2;
+ d*=eps;
+ v3_scale(&force,&distance,d);
+ v3_add(&(atom[i].f),&(atom[i].f),
+ &force);
+ }
+ } while(list_next(this)!=L_NO_NEXT_ELEMENT);
+
+ }
+ }
+ }
+
+ moldyn->energy=0.5*u;
+
+ return 0;
+}
+
+/* tersoff potential & force for 2 sorts of atoms */
+
+int tersoff(t_moldyn *moldyn) {
+
+ t_tersoff_params *params;
+ t_atom *atom,*btom,*ktom;
+ t_linkcell *lc;
+ t_list *this,*thisk,neighbour[27],neighbourk[27];
+ int i,j,k,c,ck;
+ int count;
+ double u;
+ int ni,nj,nk;
+ int ki,kj,kk;
+
+
+ params=moldyn->pot_params;
+ atom=moldyn->atom;
+ lc=&(moldyn->lc);
+ count=moldyn->count;
+
+ /* reset energy counter */
+ u=0.0;
+
+ for(i=0;i<count;i++) {
+ /* reset force */
+ v3_zero(&(atom[i].f));
+
+ /* determin cell neighbours */
+ ni=(atom[i].r.x+(moldyn->dim.x/2))/lc->x;
+ nj=(atom[i].r.y+(moldyn->dim.y/2))/lc->y;
+ nk=(atom[i].r.z+(moldyn->dim.z/2))/lc->z;
+ c=link_cell_neighbour_index(moldyn,ni,nj,nk,neighbour);
+
+ /*
+ * processing cell of atom i
+ * => no need to check for empty list (1 element at minimum)
+ */
+ this=&(neighbour[0]);
+ list_reset(this);
+ do {
+ btom=this->current->data;
+ if(btom==&(atom[i]))
+ continue;
+
+ /* 2 body stuff */
+
+ v3_sub(&dist_ij,btom,&(atom[i]));
+ d_ij=v3_norm(&dist_ij);
+ if(d_ij<=S) {
+ if(d_ij<=R) {
+ f_c=1.0;
+ df_c=0.0;
+ }
+ else {
+ s_r=S-R;
+ arg1=PI*(d_ij-R)/s_r;
+ f_c=0.5+0.5*cos(arg1);
+ df_c=-0.5*sin(arg1)*(PI/(s_r*d_ij));
+ }
+ }
+ else
+ continue;
+
+
+ /* end 2 body stuff */
+
+ /* determine cell neighbours of btom */
+ ki=(btom->r.x+(moldyn->dim.x/2))/lc->x;
+ kj=(btom->r.y+(moldyn->dim.y/2))/lc->y;
+ kk=(btom->r.z+(moldyn->dim.z/2))/lc->z;
+ ck=link_cell_neighbour_index(moldyn,ki,kj,kk,
+ neighbourk);
+
+ /* cell of btom */
+ thisk=&(neighbourk[0]);
+ list_reset(thisk);
+ do {
+ ktom=thisk->current->data;
+ if(ktom==btom)
+ continue;
+ if(ktom==&(atom[i]))
+ continue;
+
+ /* 3 body stuff (1) */
+
+ theta_ijk=;
+ sin_theta=;
+ cos_theta=;
+ hi_cos=;
+ hi_cos_square=;
+
+
+ /* end 3 body stuff (1) */
+
+
+ } while(list_next(thisk)!=L_NO_NEXT_ELEMENT);
+
+ /* direct neighbours of btom cell */
+ for(k=1;k<ck;k++) {
+ thisk=&(neighbourk[k]);
+ list_reset(thisk);
+ if(thisk->start!=NULL) {
+
+ do {
+ ktom=thisk->current->data;
+ if(ktom==&(atom[i]))
+ continue;
+
+ /* 3 body stuff (2) */
+
+ } while(list_next(thisk)!=L_NO_NEXT_ELEMENT);
+
+ }
+ }
+
+ /* indirect neighbours of btom cell */
+ for(k=ck;k<27;k++) {
+ thisk=&(neighbourk[k]);
+ list_reset(thisk);
+ if(thisk->start!=NULL) {
+
+ do {
+ ktom=thisk->current->data;
+ if(ktom==&(atom[i]))
+ continue;
+
+ /* 3 body stuff */
+
+ } while(list_next(thisk)!=L_NO_NEXT_ELEMENT);
+
+ }
+ }
+
+
+ } while(list_next(this)!=L_NO_NEXT_ELEMENT);
+
+ /*
+ * direct neighbour cells of atom i
+ */
+ for(j=1;j<c;j++) {
+ this=&(neighbour[j]);
+ list_reset(this);
+ if(this->start!=NULL) {
+
+ do {
+ btom=this->current->data;
+
+ /* 2 body stuff */
+
+
+ /* determine cell neighbours of btom */
+ ki=(btom->r.x+(moldyn->dim.x/2))/lc->x;
+ kj=(btom->r.y+(moldyn->dim.y/2))/lc->y;
+ kk=(btom->r.z+(moldyn->dim.z/2))/lc->z;
+ ck=link_cell_neighbour_index(moldyn,ki,kj,kk,
+ neighbourk);
+
+ /* cell of btom */
+ thisk=&(neighbourk[0]);
+ list_reset(thisk);
+ do {
+ ktom=thisk->current->data;
+ if(ktom==btom)
+ continue;
+ if(ktom==&(atom[i]))
+ continue;
+
+ /* 3 body stuff (1) */
+
+ } while(list_next(thisk)!=L_NO_NEXT_ELEMENT);
+
+ /* direct neighbours of btom cell */
+ for(k=1;k<ck;k++) {
+ thisk=&(neighbourk[k]);
+ list_reset(thisk);
+ if(thisk->start!=NULL) {
+
+ do {
+ ktom=thisk->current->data;
+ if(ktom==&(atom[i]))
+ continue;
+
+ /* 3 body stuff (2) */
+
+ } while(list_next(thisk)!=L_NO_NEXT_ELEMENT);
+
+ }
+ }
+
+ /* indirect neighbours of btom cell */
+ for(k=ck;k<27;k++) {
+ thisk=&(neighbourk[k]);
+ list_reset(thisk);
+ if(thisk->start!=NULL) {
+
+ do {
+ ktom=thisk->current->data;
+ if(ktom==&(atom[i]))
+ continue;
+
+ /* 3 body stuff (3) */
+
+ } while(list_next(thisk)!=L_NO_NEXT_ELEMENT);
+
+ }
+ }
+
+
+ } while(list_next(this)!=L_NO_NEXT_ELEMENT);
+
+ }
+ }
+
+ /*
+ * indirect neighbour cells of atom i
+ */
+ for(j=c;j<27;j++) {
+ this=&(neighbour[j]);
+ list_reset(this);
+ if(this->start!=NULL) {
+
+ do {
+ btom=this->current->data;
+
+ /* 2 body stuff */
+
+
+ /* determine cell neighbours of btom */
+ ki=(btom->r.x+(moldyn->dim.x/2))/lc->x;
+ kj=(btom->r.y+(moldyn->dim.y/2))/lc->y;
+ kk=(btom->r.z+(moldyn->dim.z/2))/lc->z;
+ ck=link_cell_neighbour_index(moldyn,ki,kj,kk,
+ neighbourk);
+
+ /* cell of btom */
+ thisk=&(neighbourk[0]);
+ list_reset(thisk);
+ do {
+ ktom=thisk->current->data;
+ if(ktom==btom)
+ continue;
+ if(ktom==&(atom[i]))
+ continue;
+
+ /* 3 body stuff (1) */
+
+ } while(list_next(thisk)!=L_NO_NEXT_ELEMENT);
+
+ /* direct neighbours of btom cell */
+ for(k=1;k<ck;k++) {
+ thisk=&(neighbourk[k]);
+ list_reset(thisk);
+ if(thisk->start!=NULL) {
+
+ do {
+ ktom=thisk->current->data;
+ if(ktom==&(atom[i]))
+ continue;
+
+ /* 3 body stuff (2) */
+
+ } while(list_next(thisk)!=L_NO_NEXT_ELEMENT);
+
+ }
+ }
+
+ /* indirect neighbours of btom cell */
+ for(k=ck;k<27;k++) {
+ thisk=&(neighbourk[k]);
+ list_reset(thisk);
+ if(thisk->start!=NULL) {
+
+ do {
+ ktom=thisk->current->data;
+ if(ktom==&(atom[i]))
+ continue;
+
+ /* 3 body stuff (3) */
+
+ } while(list_next(thisk)!=L_NO_NEXT_ELEMENT);
+
+ }
+ }
+
+
+ } while(list_next(this)!=L_NO_NEXT_ELEMENT);
+
+ }
+ }
+
+ }
+
+ moldyn->energy=0.5*u;
+
+ return 0;
+}
+