X-Git-Url: https://www.hackdaworld.org/gitweb/?a=blobdiff_plain;f=moldyn.c;h=d33de02efa776fa52dd3a10bbd5ca00d93ba7b4c;hb=15b4727e1137600f8f46af027aefd2b5c7a56420;hp=44b53b60b76324f441ad7c5492f942ebbd4c3195;hpb=7493af81c40106bd17811b67c6421eff7697e4ab;p=physik%2Fposic.git

diff --git a/moldyn.c b/moldyn.c
index 44b53b6..d33de02 100644
--- a/moldyn.c
+++ b/moldyn.c
@@ -17,20 +17,8 @@
 
 #include "moldyn.h"
 
-#include "math/math.h"
-#include "init/init.h"
-#include "random/random.h"
-#include "visual/visual.h"
-#include "list/list.h"
-
-
 int moldyn_init(t_moldyn *moldyn,int argc,char **argv) {
 
-	//int ret;
-
-	//ret=moldyn_parse_argv(moldyn,argc,argv);
-	//if(ret<0) return ret;
-
 	memset(moldyn,0,sizeof(t_moldyn));
 
 	rand_init(&(moldyn->random),NULL,1);
@@ -78,6 +66,13 @@ int set_temperature(t_moldyn *moldyn,double t_ref) {
 	return 0;
 }
 
+int set_pressure(t_moldyn *moldyn,double p_ref) {
+
+	moldyn->p_ref=p_ref;
+
+	return 0;
+}
+
 int set_pt_scale(t_moldyn *moldyn,u8 ptype,double ptc,u8 ttype,double ttc) {
 
 	moldyn->pt_scale=(ptype|ttype);
@@ -93,16 +88,19 @@ int set_dim(t_moldyn *moldyn,double x,double y,double z,u8 visualize) {
 	moldyn->dim.y=y;
 	moldyn->dim.z=z;
 
+	moldyn->volume=x*y*z;
+
 	if(visualize) {
 		moldyn->vis.dim.x=x;
 		moldyn->vis.dim.y=y;
 		moldyn->vis.dim.z=z;
 	}
 
-	printf("[moldyn] dimensions in A:\n");
+	printf("[moldyn] dimensions in A and A^3 respectively:\n");
 	printf("  x: %f\n",moldyn->dim.x);
 	printf("  y: %f\n",moldyn->dim.y);
 	printf("  z: %f\n",moldyn->dim.z);
+	printf("  volume: %f\n",moldyn->volume);
 	printf("  visualize simulation box: %s\n",visualize?"on":"off");
 
 	return 0;
@@ -227,34 +225,43 @@ int moldyn_log_shutdown(t_moldyn *moldyn) {
 	return 0;
 }
 
+/*
+ * creating lattice functions
+ */
+
 int create_lattice(t_moldyn *moldyn,u8 type,double lc,int element,double mass,
-                   u8 attr,u8 bnum,int a,int b,int c) {
+                   u8 attr,u8 brand,int a,int b,int c) {
 
-	int count;
+	int new,count;
 	int ret;
 	t_3dvec origin;
+	void *ptr;
+	t_atom *atom;
 
-	count=a*b*c;
+	new=a*b*c;
+	count=moldyn->count;
 
 	/* how many atoms do we expect */
-	if(type==FCC) count*=4;
-	if(type==DIAMOND) count*=8;
+	if(type==FCC) new*=4;
+	if(type==DIAMOND) new*=8;
 
 	/* allocate space for atoms */
-	moldyn->atom=malloc(count*sizeof(t_atom));
-	if(moldyn->atom==NULL) {
-		perror("malloc (atoms)");
+	ptr=realloc(moldyn->atom,(count+new)*sizeof(t_atom));
+	if(!ptr) {
+		perror("[moldyn] realloc (create lattice)");
 		return -1;
 	}
-
+	moldyn->atom=ptr;
+	atom=&(moldyn->atom[count]);
+		
 	v3_zero(&origin);
 
 	switch(type) {
 		case FCC:
-			ret=fcc_init(a,b,c,lc,moldyn->atom,&origin);
+			ret=fcc_init(a,b,c,lc,atom,&origin);
 			break;
 		case DIAMOND:
-			ret=diamond_init(a,b,c,lc,moldyn->atom,&origin);
+			ret=diamond_init(a,b,c,lc,atom,&origin);
 			break;
 		default:
 			printf("unknown lattice type (%02x)\n",type);
@@ -262,30 +269,114 @@ int create_lattice(t_moldyn *moldyn,u8 type,double lc,int element,double mass,
 	}
 
 	/* debug */
-	if(ret!=count) {
+	if(ret!=new) {
 		printf("[moldyn] creating lattice failed\n");
 		printf("  amount of atoms\n");
-		printf("  - expected: %d\n",count);
+		printf("  - expected: %d\n",new);
 		printf("  - created: %d\n",ret);
 		return -1;
 	}
 
-	moldyn->count=count;
-	printf("[moldyn] created lattice with %d atoms\n",count);
+	moldyn->count+=new;
+	printf("[moldyn] created lattice with %d atoms\n",new);
 
-	while(count) {
-		count-=1;
-		moldyn->atom[count].element=element;
-		moldyn->atom[count].mass=mass;
-		moldyn->atom[count].attr=attr;
-		moldyn->atom[count].bnum=bnum;
-		check_per_bound(moldyn,&(moldyn->atom[count].r));
+	for(ret=0;ret<new;ret++) {
+		atom[ret].element=element;
+		atom[ret].mass=mass;
+		atom[ret].attr=attr;
+		atom[ret].brand=brand;
+		atom[ret].tag=count+ret;
+		check_per_bound(moldyn,&(atom[ret].r));
 	}
 
 	return ret;
 }
 
-int add_atom(t_moldyn *moldyn,int element,double mass,u8 bnum,u8 attr,
+/* fcc lattice init */
+int fcc_init(int a,int b,int c,double lc,t_atom *atom,t_3dvec *origin) {
+
+	int count;
+	int i,j;
+	t_3dvec o,r,n;
+	t_3dvec basis[3];
+	double help[3];
+	double x,y,z;
+
+	x=a*lc;
+	y=b*lc;
+	z=c*lc;
+
+	if(origin) v3_copy(&o,origin);
+	else v3_zero(&o);
+
+	/* construct the basis */
+	for(i=0;i<3;i++) {
+		for(j=0;j<3;j++) {
+			if(i!=j) help[j]=0.5*lc;
+			else help[j]=.0;
+		}
+		v3_set(&basis[i],help);
+	}
+
+	v3_zero(&r);
+	count=0;
+	
+	/* fill up the room */
+	r.x=o.x;
+	while(r.x<x) {
+		r.y=o.y;
+		while(r.y<y) {
+			r.z=o.z;
+			while(r.z<z) {
+				v3_copy(&(atom[count].r),&r);
+				atom[count].element=1;
+				count+=1;
+				for(i=0;i<3;i++) {
+					v3_add(&n,&r,&basis[i]);
+					if((n.x<x+o.x)&&
+					   (n.y<y+o.y)&&
+					   (n.z<z+o.z)) {
+						v3_copy(&(atom[count].r),&n);
+						count+=1;
+					}
+				}
+				r.z+=lc;	
+			}
+			r.y+=lc;
+		}
+		r.x+=lc;
+	}
+
+	/* coordinate transformation */
+	help[0]=x/2.0;
+	help[1]=y/2.0;
+	help[2]=z/2.0;
+	v3_set(&n,help);
+	for(i=0;i<count;i++)
+		v3_sub(&(atom[i].r),&(atom[i].r),&n);
+		
+	return count;
+}
+
+int diamond_init(int a,int b,int c,double lc,t_atom *atom,t_3dvec *origin) {
+
+	int count;
+	t_3dvec o;
+
+	count=fcc_init(a,b,c,lc,atom,origin);
+
+	o.x=0.25*lc;
+	o.y=0.25*lc;
+	o.z=0.25*lc;
+
+	if(origin) v3_add(&o,&o,origin);
+
+	count+=fcc_init(a,b,c,lc,&atom[count],&o);
+
+	return count;
+}
+
+int add_atom(t_moldyn *moldyn,int element,double mass,u8 brand,u8 attr,
              t_3dvec *r,t_3dvec *v) {
 
 	t_atom *atom;
@@ -293,9 +384,9 @@ int add_atom(t_moldyn *moldyn,int element,double mass,u8 bnum,u8 attr,
 	int count;
 	
 	atom=moldyn->atom;
-	count=++(moldyn->count);
+	count=(moldyn->count)++;
 
-	ptr=realloc(atom,count*sizeof(t_atom));
+	ptr=realloc(atom,(count+1)*sizeof(t_atom));
 	if(!ptr) {
 		perror("[moldyn] realloc (add atom)");
 		return -1;
@@ -303,12 +394,13 @@ int add_atom(t_moldyn *moldyn,int element,double mass,u8 bnum,u8 attr,
 	moldyn->atom=ptr;
 
 	atom=moldyn->atom;
-	atom[count-1].r=*r;
-	atom[count-1].v=*v;
-	atom[count-1].element=element;
-	atom[count-1].mass=mass;
-	atom[count-1].bnum=bnum;
-	atom[count-1].attr=attr;
+	atom[count].r=*r;
+	atom[count].v=*v;
+	atom[count].element=element;
+	atom[count].mass=mass;
+	atom[count].brand=brand;
+	atom[count].tag=count;
+	atom[count].attr=attr;
 
 	return 0;
 }
@@ -368,6 +460,28 @@ int thermal_init(t_moldyn *moldyn,u8 equi_init) {
 	return 0;
 }
 
+double temperature_calc(t_moldyn *moldyn) {
+
+	double double_ekin;
+	int i;
+	t_atom *atom;
+
+	atom=moldyn->atom;
+
+	for(i=0;i<moldyn->count;i++)
+		double_ekin+=atom[i].mass*v3_absolute_square(&(atom[i].v));
+
+	/* kinetic energy = 3/2 N k_B T */
+	moldyn->t=double_ekin/(3.0*K_BOLTZMANN*moldyn->count);
+
+	return moldyn->t;
+}
+
+double get_temperature(t_moldyn *moldyn) {
+
+	return moldyn->t;
+}
+
 int scale_velocity(t_moldyn *moldyn,u8 equi_init) {
 
 	int i;
@@ -386,11 +500,12 @@ int scale_velocity(t_moldyn *moldyn,u8 equi_init) {
 	count=0;
 	for(i=0;i<moldyn->count;i++) {
 		if((equi_init&TRUE)||(atom[i].attr&ATOM_ATTR_HB)) {
-			e+=0.5*atom[i].mass*v3_absolute_square(&(atom[i].v));
+			e+=atom[i].mass*v3_absolute_square(&(atom[i].v));
 			count+=1;
 		}
 	}
-	if(count!=0) moldyn->t=(2.0*e)/(3.0*count*K_BOLTZMANN);
+	e*=0.5;
+	if(count!=0) moldyn->t=e/(1.5*count*K_BOLTZMANN);
 	else return 0;	/* no atoms involved in scaling! */
 	
 	/* (temporary) hack for e,t = 0 */
@@ -423,6 +538,97 @@ int scale_velocity(t_moldyn *moldyn,u8 equi_init) {
 	return 0;
 }
 
+double pressure_calc(t_moldyn *moldyn) {
+
+	int i;
+	t_atom *atom;
+	double p1,p2,p=0;
+	
+	for(i=0;i<moldyn->count;i++) {
+		
+
+	}
+
+	p1=(moldyn->count*K_BOLTZMANN*moldyn->t-ONE_THIRD*moldyn->vt1);
+	p1/=moldyn->volume;
+
+	p2=(moldyn->count*K_BOLTZMANN*moldyn->t-ONE_THIRD*moldyn->vt2);
+	p2/=moldyn->volume;
+
+	printf("compare pressures: %f %f\n",p1/ATM,p2/ATM);
+
+	return moldyn->p;
+}	
+
+double get_pressure(t_moldyn *moldyn) {
+
+	return moldyn->p;
+
+}
+
+int scale_volume(t_moldyn *moldyn) {
+
+	t_atom *atom;
+	t_3dvec *dim,*vdim;
+	double scale,v;
+	t_virial virial;
+	t_linkcell *lc;
+	int i;
+
+	atom=moldyn->atom;
+	dim=&(moldyn->dim);
+	vdim=&(moldyn->vis.dim);
+	lc=&(moldyn->lc);
+
+	memset(&virial,0,sizeof(t_virial));
+
+	for(i=0;i<moldyn->count;i++) {
+		virial.xx+=atom[i].virial.xx;
+		virial.yy+=atom[i].virial.yy;
+		virial.zz+=atom[i].virial.zz;
+		virial.xy+=atom[i].virial.xy;
+		virial.xz+=atom[i].virial.xz;
+		virial.yz+=atom[i].virial.yz;
+	}
+
+	/* just a guess so far ... */
+	v=virial.xx+virial.yy+virial.zz;
+
+printf("%f\n",v);
+	/* get pressure from virial */
+	moldyn->p=moldyn->count*K_BOLTZMANN*moldyn->t+ONE_THIRD*v;
+	moldyn->p/=moldyn->volume;
+printf("%f | %f\n",moldyn->p/(ATM),moldyn->p_ref/ATM);
+
+	/* scale factor */
+	if(moldyn->pt_scale&P_SCALE_BERENDSEN)
+		scale=3*sqrt(1-(moldyn->p_ref-moldyn->p)/moldyn->p_tc);
+	else 
+		/* should actually never be used */
+		scale=pow(moldyn->p/moldyn->p_ref,1.0/3.0);
+
+printf("scale = %f\n",scale);
+	/* actual scaling */
+	dim->x*=scale;
+	dim->y*=scale;
+	dim->z*=scale;
+	if(vdim->x) vdim->x=dim->x;
+	if(vdim->y) vdim->y=dim->y;
+	if(vdim->z) vdim->z=dim->z;
+	moldyn->volume*=(scale*scale*scale);
+
+	/* check whether we need a new linkcell init */
+	if((dim->x/moldyn->cutoff!=lc->nx)||
+	   (dim->y/moldyn->cutoff!=lc->ny)||
+	   (dim->z/moldyn->cutoff!=lc->nx)) {
+		link_cell_shutdown(moldyn);
+		link_cell_init(moldyn);
+	}
+
+	return 0;
+
+}
+
 double get_e_kin(t_moldyn *moldyn) {
 
 	int i;
@@ -437,11 +643,6 @@ double get_e_kin(t_moldyn *moldyn) {
 	return moldyn->ekin;
 }
 
-double get_e_pot(t_moldyn *moldyn) {
-
-	return moldyn->energy;
-}
-
 double update_e_kin(t_moldyn *moldyn) {
 
 	return(get_e_kin(moldyn));
@@ -490,9 +691,6 @@ int link_cell_init(t_moldyn *moldyn) {
 
 	t_linkcell *lc;
 	int i;
-	int fd;
-
-	fd=open("/dev/null",O_WRONLY);
 
 	lc=&(moldyn->lc);
 
@@ -507,11 +705,13 @@ int link_cell_init(t_moldyn *moldyn) {
 	lc->cells=lc->nx*lc->ny*lc->nz;
 	lc->subcell=malloc(lc->cells*sizeof(t_list));
 
+	if(lc->cells<27)
+		printf("[moldyn] FATAL: less then 27 subcells!\n");
+
 	printf("[moldyn] 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]),fd);
+		list_init_f(&(lc->subcell[i]));
 
  	link_cell_update(moldyn);
 	
@@ -521,26 +721,30 @@ int link_cell_init(t_moldyn *moldyn) {
 int link_cell_update(t_moldyn *moldyn) {
 
 	int count,i,j,k;
-	int nx,ny,nz;
+	int nx,ny;
 	t_atom *atom;
 	t_linkcell *lc;
+	double x,y,z;
 
 	atom=moldyn->atom;
 	lc=&(moldyn->lc);
 
 	nx=lc->nx;
 	ny=lc->ny;
-	nz=lc->nz;
+
+	x=moldyn->dim.x/2;
+	y=moldyn->dim.y/2;
+	z=moldyn->dim.z/2;
 
 	for(i=0;i<lc->cells;i++)
-		list_destroy(&(moldyn->lc.subcell[i]));
+		list_destroy_f(&(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]));
+		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_f(&(moldyn->lc.subcell[i+j*nx+k*nx*ny]),
+		                     &(atom[count]));
 	}
 
 	return 0;
@@ -610,7 +814,9 @@ int link_cell_shutdown(t_moldyn *moldyn) {
 	lc=&(moldyn->lc);
 
 	for(i=0;i<lc->nx*lc->ny*lc->nz;i++)
-		list_shutdown(&(moldyn->lc.subcell[i]));
+		list_destroy_f(&(moldyn->lc.subcell[i]));
+
+	free(lc->subcell);
 
 	return 0;
 }
@@ -622,23 +828,23 @@ int moldyn_add_schedule(t_moldyn *moldyn,int runs,double tau) {
 	t_moldyn_schedule *schedule;
 
 	schedule=&(moldyn->schedule);
-	count=++(schedule->content_count);
+	count=++(schedule->total_sched);
 
-	ptr=realloc(moldyn->schedule.runs,count*sizeof(int));
+	ptr=realloc(schedule->runs,count*sizeof(int));
 	if(!ptr) {
 		perror("[moldyn] realloc (runs)");
 		return -1;
 	}
-	moldyn->schedule.runs=ptr;
-	moldyn->schedule.runs[count-1]=runs;
+	schedule->runs=ptr;
+	schedule->runs[count-1]=runs;
 
 	ptr=realloc(schedule->tau,count*sizeof(double));
 	if(!ptr) {
 		perror("[moldyn] realloc (tau)");
 		return -1;
 	}
-	moldyn->schedule.tau=ptr;
-	moldyn->schedule.tau[count-1]=tau;
+	schedule->tau=ptr;
+	schedule->tau[count-1]=tau;
 
 	return 0;
 }
@@ -661,16 +867,16 @@ int moldyn_set_schedule_hook(t_moldyn *moldyn,void *hook,void *hook_params) {
 
 int moldyn_integrate(t_moldyn *moldyn) {
 
-	int i,sched;
+	int i;
 	unsigned int e,m,s,v;
 	t_3dvec p;
-	t_moldyn_schedule *schedule;
+	t_moldyn_schedule *sched;
 	t_atom *atom;
 	int fd;
 	char dir[128];
 	double ds;
 
-	schedule=&(moldyn->schedule);
+	sched=&(moldyn->schedule);
 	atom=moldyn->atom;
 
 	/* initialize linked cell method */
@@ -707,12 +913,12 @@ int moldyn_integrate(t_moldyn *moldyn) {
 	moldyn->debug=0;
 
 	/* executing the schedule */
-	for(sched=0;sched<moldyn->schedule.content_count;sched++) {
+	for(sched->count=0;sched->count<sched->total_sched;sched->count++) {
 
 		/* setting amount of runs and finite time step size */
-		moldyn->tau=schedule->tau[sched];
+		moldyn->tau=sched->tau[sched->count];
 		moldyn->tau_square=moldyn->tau*moldyn->tau;
-		moldyn->time_steps=schedule->runs[sched];
+		moldyn->time_steps=sched->runs[sched->count];
 
 	/* integration according to schedule */
 
@@ -724,15 +930,25 @@ int moldyn_integrate(t_moldyn *moldyn) {
 		/* p/t scaling */
 		if(moldyn->pt_scale&(T_SCALE_BERENDSEN|T_SCALE_DIRECT))
 			scale_velocity(moldyn,FALSE);
+		if(moldyn->pt_scale&(P_SCALE_BERENDSEN|P_SCALE_DIRECT))
+			scale_volume(moldyn);
 
 		/* check for log & visualization */
+//double ax;
+//double ao;
+//double av;
 		if(e) {
 			if(!(i%e))
+//ao=sqrt(0.1/M_SI);
+//ax=((0.28-0.25)*sqrt(3)*LC_SI/2)*cos(ao*i);
+//av=ao*(0.28-0.25)*sqrt(3)*LC_SI/2*sin(ao*i);
+				update_e_kin(moldyn);
 				dprintf(moldyn->efd,
 				        "%f %f %f %f\n",
-				        moldyn->time,update_e_kin(moldyn),
+				        moldyn->time,moldyn->ekin,
 				        moldyn->energy,
 				        get_total_energy(moldyn));
+//moldyn->atom[0].r.x,ax,av*av*M_SI,0.1*ax*ax,av*av*M_SI+0.1*ax*ax);
 		}
 		if(m) {
 			if(!(i%m)) {
@@ -760,7 +976,7 @@ int moldyn_integrate(t_moldyn *moldyn) {
 				visual_atoms(&(moldyn->vis),moldyn->time,
 				             moldyn->atom,moldyn->count);
 				printf("\rsched: %d, steps: %d, debug: %d",
-				       sched,i,moldyn->debug);
+				       sched->count,i,moldyn->debug);
 				fflush(stdout);
 			}
 		}
@@ -771,8 +987,8 @@ int moldyn_integrate(t_moldyn *moldyn) {
 	}
 
 		/* check for hooks */
-		if(schedule->hook)
-			schedule->hook(moldyn,schedule->hook_params);
+		if(sched->hook)
+			sched->hook(moldyn,sched->hook_params);
 
 		/* get a new info line */
 		printf("\n");
@@ -787,7 +1003,7 @@ int moldyn_integrate(t_moldyn *moldyn) {
 int velocity_verlet(t_moldyn *moldyn) {
 
 	int i,count;
-	double tau,tau_square;
+	double tau,tau_square,h;
 	t_3dvec delta;
 	t_atom *atom;
 
@@ -798,18 +1014,18 @@ int velocity_verlet(t_moldyn *moldyn) {
 
 	for(i=0;i<count;i++) {
 		/* new positions */
+		h=0.5/atom[i].mass;
 		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_scale(&delta,&(atom[i].f),h*tau_square);
 		v3_add(&(atom[i].r),&(atom[i].r),&delta);
 		check_per_bound(moldyn,&(atom[i].r));
 
-		/* velocities */
-		v3_scale(&delta,&(atom[i].f),0.5*tau/atom[i].mass);
+		/* velocities [actually v(t+tau/2)] */
+		v3_scale(&delta,&(atom[i].f),h*tau);
 		v3_add(&(atom[i].v),&(atom[i].v),&delta);
 	}
 
-moldyn_bc_check(moldyn);
 	/* neighbour list update */
 	link_cell_update(moldyn);
 
@@ -817,7 +1033,7 @@ moldyn_bc_check(moldyn);
 	potential_force_calc(moldyn);
 
 	for(i=0;i<count;i++) {
-		/* again velocities */
+		/* again velocities [actually v(t+tau)] */
 		v3_scale(&delta,&(atom[i].f),0.5*tau/atom[i].mass);
 		v3_add(&(atom[i].v),&(atom[i].v),&delta);
 	}
@@ -828,7 +1044,7 @@ moldyn_bc_check(moldyn);
 
 /*
  *
- * potentials & corresponding forces
+ * potentials & corresponding forces & virial routine
  * 
  */
 
@@ -838,10 +1054,10 @@ int potential_force_calc(t_moldyn *moldyn) {
 
 	int i,j,k,count;
 	t_atom *itom,*jtom,*ktom;
+	t_virial *virial;
 	t_linkcell *lc;
 	t_list neighbour_i[27];
 	t_list neighbour_i2[27];
-	//t_list neighbour_j[27];
 	t_list *this,*that;
 	u8 bc_ij,bc_ik;
 	int dnlc;
@@ -853,12 +1069,27 @@ int potential_force_calc(t_moldyn *moldyn) {
 	/* reset energy */
 	moldyn->energy=0.0;
 
+	moldyn->vt2=0.0;
+	
 	/* get energy and force of every atom */
 	for(i=0;i<count;i++) {
 
 		/* reset force */
 		v3_zero(&(itom[i].f));
 
+		/* reset viral of atom i */
+		virial=&(itom[i].virial);
+		virial->xx=0.0;
+		virial->yy=0.0;
+		virial->zz=0.0;
+		virial->xy=0.0;
+		virial->xz=0.0;
+		virial->yz=0.0;
+		moldyn->vt1=0.0;
+
+		/* reset site energy */
+		itom[i].e=0.0;
+
 		/* single particle potential/force */
 		if(itom[i].attr&ATOM_ATTR_1BP)
 			moldyn->func1b(moldyn,&(itom[i]));
@@ -879,7 +1110,7 @@ int potential_force_calc(t_moldyn *moldyn) {
 		for(j=0;j<27;j++) {
 
 			this=&(neighbour_i[j]);
-			list_reset(this);
+			list_reset_f(this);
 
 			if(this->start==NULL)
 				continue;
@@ -914,7 +1145,7 @@ int potential_force_calc(t_moldyn *moldyn) {
 				for(k=0;k<27;k++) {
 
 					that=&(neighbour_i2[k]);
-					list_reset(that);
+					list_reset_f(that);
 					
 					if(that->start==NULL)
 						continue;
@@ -940,7 +1171,7 @@ int potential_force_calc(t_moldyn *moldyn) {
 						               ktom,
 						               bc_ik|bc_ij);
 
-					} while(list_next(that)!=\
+					} while(list_next_f(that)!=\
 					        L_NO_NEXT_ELEMENT);
 
 				}
@@ -952,11 +1183,41 @@ int potential_force_calc(t_moldyn *moldyn) {
 					                    jtom,bc_ij);
 				}
 					
-			} while(list_next(this)!=L_NO_NEXT_ELEMENT);
+			} while(list_next_f(this)!=L_NO_NEXT_ELEMENT);
 		
 		}
 
 	}
+#ifdef DEBUG
+printf("\n\n");
+#endif
+#ifdef VDEBUG
+printf("\n\n");
+#endif
+
+	moldyn->vt2=0.0;
+	for(i=0;i<count;i++)
+		moldyn->vt2-=v3_scalar_product(&(itom[i].r),&(itom[i].f));
+
+printf("compare: vt1: %f vt2: %f\n",moldyn->vt1,moldyn->vt2);
+
+pressure_calc(moldyn);
+
+	return 0;
+}
+
+/*
+ * virial calculation
+ */
+
+inline int virial_calc(t_atom *a,t_3dvec *f,t_3dvec *d) {
+
+	a->virial.xx-=f->x*d->x;
+	a->virial.yy-=f->y*d->y;
+	a->virial.zz-=f->z*d->z;
+	a->virial.xy-=f->x*d->y;
+	a->virial.xz-=f->x*d->z;
+	a->virial.yz-=f->y*d->z;
 
 	return 0;
 }
@@ -965,7 +1226,7 @@ int potential_force_calc(t_moldyn *moldyn) {
  * periodic boundayr checking
  */
 
-int check_per_bound(t_moldyn *moldyn,t_3dvec *a) {
+inline int check_per_bound(t_moldyn *moldyn,t_3dvec *a) {
 	
 	double x,y,z;
 	t_3dvec *dim;
@@ -988,7 +1249,6 @@ int check_per_bound(t_moldyn *moldyn,t_3dvec *a) {
 		if(a->z>=z) a->z-=dim->z;
 		else if(-a->z>z) a->z+=dim->z;
 	}
-printf("%f %f %f\n",a->x,x,a->x/x);
 
 	return 0;
 }
@@ -1004,23 +1264,29 @@ int harmonic_oscillator(t_moldyn *moldyn,t_atom *ai,t_atom *aj,u8 bc) {
 
 	t_ho_params *params;
 	t_3dvec force,distance;
-	double d;
+	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) {
-		/* energy is 1/2 (d-d0)^2, but we will add this twice ... */
-		moldyn->energy+=(0.25*sc*(d-equi_dist)*(d-equi_dist));
+		moldyn->energy+=(0.5*sc*(d-equi_dist)*(d-equi_dist));
 		/* f = -grad E; grad r_ij = -1 1/r_ij distance */
-		v3_scale(&force,&distance,sc*(1.0-(equi_dist/d)));
+		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;
@@ -1040,6 +1306,8 @@ int lennard_jones(t_moldyn *moldyn,t_atom *ai,t_atom *aj,u8 bc) {
 	sig6=params->sigma6;
 	sig12=params->sigma12;
 
+	if(ai<aj) return 0;
+
 	v3_sub(&distance,&(aj->r),&(ai->r));
 	if(bc) check_per_bound(moldyn,&distance);
 	d=v3_absolute_square(&distance);	/* 1/r^2 */
@@ -1048,16 +1316,20 @@ int lennard_jones(t_moldyn *moldyn,t_atom *ai,t_atom *aj,u8 bc) {
 		h2=d*d; 			/* 1/r^4 */
 		h2*=d;	 			/* 1/r^6 */
 		h1=h2*h2; 			/* 1/r^12 */
-		/* energy is eps*..., but we will add this twice ... */
-		moldyn->energy+=0.5*eps*(sig12*h1-sig6*h2);
+		moldyn->energy+=(eps*(sig12*h1-sig6*h2)-params->uc);
 		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(&(aj->f),&(aj->f),&force);
 		v3_scale(&force,&distance,-1.0*d); /* f = - grad E */
 		v3_add(&(ai->f),&(ai->f),&force);
+		virial_calc(ai,&force,&distance);
+		virial_calc(aj,&force,&distance); /* f and d signe switched */
+		moldyn->vt1-=v3_scalar_product(&force,&distance);
 	}
 
 	return 0;
@@ -1071,7 +1343,10 @@ int lennard_jones(t_moldyn *moldyn,t_atom *ai,t_atom *aj,u8 bc) {
 int tersoff_mult_complete_params(t_tersoff_mult_params *p) {
 
 	printf("[moldyn] tersoff parameter completion\n");
+	p->S2[0]=p->S[0]*p->S[0];
+	p->S2[1]=p->S[1]*p->S[1];
 	p->Smixed=sqrt(p->S[0]*p->S[1]);
+	p->S2mixed=p->Smixed*p->Smixed;
 	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]);
@@ -1099,11 +1374,11 @@ int tersoff_mult_complete_params(t_tersoff_mult_params *p) {
 /* tersoff 1 body part */
 int tersoff_mult_1bp(t_moldyn *moldyn,t_atom *ai) {
 
-	int num;
+	int brand;
 	t_tersoff_mult_params *params;
 	t_tersoff_exchange *exchange;
 	
-	num=ai->bnum;
+	brand=ai->brand;
 	params=moldyn->pot1b_params;
 	exchange=&(params->exchange);
 
@@ -1112,15 +1387,15 @@ int tersoff_mult_1bp(t_moldyn *moldyn,t_atom *ai) {
 	 *         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->beta_i=&(params->beta[brand]);
+	exchange->n_i=&(params->n[brand]);
+	exchange->c_i=&(params->c[brand]);
+	exchange->d_i=&(params->d[brand]);
+	exchange->h_i=&(params->h[brand]);
 
 	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->ci2=params->c[brand]*params->c[brand];
+	exchange->di2=params->d[brand]*params->d[brand];
 	exchange->ci2di2=exchange->ci2/exchange->di2;
 
 	return 0;
@@ -1132,16 +1407,16 @@ 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 d_ij,d_ij2;
+	double A,B,R,S,S2,lambda,mu;
 	double f_r,df_r;
 	double f_c,df_c;
-	int num;
+	int brand;
 	double s_r;
 	double arg;
 
 	params=moldyn->pot2b_params;
-	num=aj->bnum;
+	brand=aj->brand;
 	exchange=&(params->exchange);
 
 	/* clear 3bp and 2bp post run */
@@ -1164,27 +1439,20 @@ int tersoff_mult_2bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,u8 bc) {
 	 *
 	 */
 
-	/* 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];
+	if(brand==ai->brand) {
+		S=params->S[brand];
+		S2=params->S2[brand];
+		R=params->R[brand];
+		A=params->A[brand];
+		B=params->B[brand];
+		lambda=params->lambda[brand];
+		mu=params->mu[brand];
 		exchange->chi=1.0;
 	}
 	else {
 		S=params->Smixed;
+		S2=params->S2mixed;
 		R=params->Rmixed;
 		A=params->Amixed;
 		B=params->Bmixed;
@@ -1193,17 +1461,31 @@ int tersoff_mult_2bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,u8 bc) {
 		params->exchange.chi=params->chi;
 	}
 
-	/* if d_ij > S => no force & potential energy contribution */
-	if(d_ij>S)
+	/* dist_ij, d_ij */
+	v3_sub(&dist_ij,&(aj->r),&(ai->r));
+	if(bc) check_per_bound(moldyn,&dist_ij);
+	d_ij2=v3_absolute_square(&dist_ij);
+
+	/* if d_ij2 > S2 => no force & potential energy contribution */
+	if(d_ij2>S2)
 		return 0;
 
+	/* now we will need the distance */
+	//d_ij=v3_norm(&dist_ij);
+	d_ij=sqrt(d_ij2);
+
+	/* save for use in 3bp */
+	exchange->d_ij=d_ij;
+	exchange->d_ij2=d_ij2;
+	exchange->dist_ij=dist_ij;
+
 	/* 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->beta_j=&(params->beta[brand]);
+	exchange->n_j=&(params->n[brand]);
+	exchange->c_j=&(params->c[brand]);
+	exchange->d_j=&(params->d[brand]);
+	exchange->h_j=&(params->h[brand]);
+	if(brand==ai->brand) {
 		exchange->betajnj=exchange->betaini;
 		exchange->cj2=exchange->ci2;
 		exchange->dj2=exchange->di2;
@@ -1211,8 +1493,8 @@ int tersoff_mult_2bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,u8 bc) {
 	}
 	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->cj2=params->c[brand]*params->c[brand];
+		exchange->dj2=params->d[brand]*params->d[brand];
 		exchange->cj2dj2=exchange->cj2/exchange->dj2;
 	}
 
@@ -1236,7 +1518,7 @@ int tersoff_mult_2bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,u8 bc) {
 		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));
+		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 */
@@ -1247,6 +1529,31 @@ int tersoff_mult_2bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,u8 bc) {
 	 * dVij = dVji and we sum up both: no 1/2) */
 	v3_add(&(ai->f),&(ai->f),&force);
 
+	/* virial */
+	ai->virial.xx-=force.x*dist_ij.x;
+	ai->virial.yy-=force.y*dist_ij.y;
+	ai->virial.zz-=force.z*dist_ij.z;
+	ai->virial.xy-=force.x*dist_ij.y;
+	ai->virial.xz-=force.x*dist_ij.z;
+	ai->virial.yz-=force.y*dist_ij.z;
+
+#ifdef DEBUG
+if(ai==&(moldyn->atom[0])) {
+	printf("dVij, dVji (2bp) contrib:\n");
+	printf("%f | %f\n",force.x,ai->f.x);
+	printf("%f | %f\n",force.y,ai->f.y);
+	printf("%f | %f\n",force.z,ai->f.z);
+}
+#endif
+#ifdef VDEBUG
+if(ai==&(moldyn->atom[0])) {
+	printf("dVij, dVji (2bp) contrib:\n");
+	printf("%f | %f\n",force.x*dist_ij.x,ai->virial.xx);
+	printf("%f | %f\n",force.y*dist_ij.y,ai->virial.yy);
+	printf("%f | %f\n",force.z*dist_ij.z,ai->virial.zz);
+}
+#endif
+
 	/* energy 2bp contribution (ij, ji) is 0.5 f_r f_c ... */
 	moldyn->energy+=(0.5*f_r*f_c);
 
@@ -1316,7 +1623,6 @@ int tersoff_mult_post_2bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,u8 bc) {
 	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);
 	}
@@ -1338,6 +1644,31 @@ int tersoff_mult_post_2bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,u8 bc) {
 	/* add force */
 	v3_add(&(ai->f),&(ai->f),&force);
 
+	/* virial */
+	ai->virial.xx-=force.x*dist_ij->x;
+	ai->virial.yy-=force.y*dist_ij->y;
+	ai->virial.zz-=force.z*dist_ij->z;
+	ai->virial.xy-=force.x*dist_ij->y;
+	ai->virial.xz-=force.x*dist_ij->z;
+	ai->virial.yz-=force.y*dist_ij->z;
+
+#ifdef DEBUG
+if(ai==&(moldyn->atom[0])) {
+	printf("dVij (3bp) contrib:\n");
+	printf("%f | %f\n",force.x,ai->f.x);
+	printf("%f | %f\n",force.y,ai->f.y);
+	printf("%f | %f\n",force.z,ai->f.z);
+}
+#endif
+#ifdef VDEBUG
+if(ai==&(moldyn->atom[0])) {
+	printf("dVij (3bp) contrib:\n");
+	printf("%f | %f\n",force.x*dist_ij->x,ai->virial.xx);
+	printf("%f | %f\n",force.y*dist_ij->y,ai->virial.yy);
+	printf("%f | %f\n",force.z*dist_ij->z,ai->virial.zz);
+}
+#endif
+
 	/* add energy of 3bp sum */
 	moldyn->energy+=(0.5*f_c*b*f_a);
 
@@ -1366,6 +1697,32 @@ int tersoff_mult_post_2bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,u8 bc) {
 	/* add force */
 	v3_add(&(ai->f),&(ai->f),&force);
 
+	/* virial - plus sign, as dist_ij = - dist_ji - (really??) */
+// TEST ... with a minus instead
+	ai->virial.xx-=force.x*dist_ij->x;
+	ai->virial.yy-=force.y*dist_ij->y;
+	ai->virial.zz-=force.z*dist_ij->z;
+	ai->virial.xy-=force.x*dist_ij->y;
+	ai->virial.xz-=force.x*dist_ij->z;
+	ai->virial.yz-=force.y*dist_ij->z;
+
+#ifdef DEBUG
+if(ai==&(moldyn->atom[0])) {
+	printf("dVji (3bp) contrib:\n");
+	printf("%f | %f\n",force.x,ai->f.x);
+	printf("%f | %f\n",force.y,ai->f.y);
+	printf("%f | %f\n",force.z,ai->f.z);
+}
+#endif
+#ifdef VDEBUG
+if(ai==&(moldyn->atom[0])) {
+	printf("dVji (3bp) contrib:\n");
+	printf("%f | %f\n",force.x*dist_ij->x,ai->virial.xx);
+	printf("%f | %f\n",force.y*dist_ij->y,ai->virial.yy);
+	printf("%f | %f\n",force.z*dist_ij->z,ai->virial.zz);
+}
+#endif
+
 	return 0;
 }
 
@@ -1378,9 +1735,9 @@ int tersoff_mult_3bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,t_atom *ak,u8 bc) {
 	t_3dvec dist_ij,dist_ik,dist_jk;
 	t_3dvec temp1,temp2;
 	t_3dvec *dzeta;
-	double R,S,s_r;
+	double R,S,S2,s_r;
 	double B,mu;
-	double d_ij,d_ik,d_jk;
+	double d_ij,d_ik,d_jk,d_ij2,d_ik2,d_jk2;
 	double rr,dd;
 	double f_c,df_c;
 	double f_c_ik,df_c_ik,arg;
@@ -1391,7 +1748,7 @@ int tersoff_mult_3bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,t_atom *ak,u8 bc) {
 	double h_cos,d2_h_cos2;
 	double frac,g,zeta,chi;
 	double tmp;
-	int num;
+	int brand;
 
 	params=moldyn->pot3b_params;
 	exchange=&(params->exchange);
@@ -1426,6 +1783,7 @@ int tersoff_mult_3bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,t_atom *ak,u8 bc) {
 	/* dist_ij, d_ij - this is < S_ij ! */
 	dist_ij=exchange->dist_ij;
 	d_ij=exchange->d_ij;
+	d_ij2=exchange->d_ij2;
 
 	/* f_c_ij, df_c_ij (same for ji) */
 	f_c=exchange->f_c;
@@ -1440,21 +1798,26 @@ int tersoff_mult_3bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,t_atom *ak,u8 bc) {
 	/* 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);
+	d_ik2=v3_absolute_square(&dist_ik);
 
 	/* ik constants */
-	num=ai->bnum;
-	if(num==ak->bnum) {
-		R=params->R[num];
-		S=params->S[num];
+	brand=ai->brand;
+	if(brand==ak->brand) {
+		R=params->R[brand];
+		S=params->S[brand];
+		S2=params->S2[brand];
 	}
 	else {
 		R=params->Rmixed;
 		S=params->Smixed;
+		S2=params->S2mixed;
 	}
 
 	/* zeta_ij/dzeta_ij contribution only for d_ik < S */
-	if(d_ik<S) {
+	if(d_ik2<S2) {
+
+		/* now we need d_ik */
+		d_ik=sqrt(d_ik2);
 
 		/* get constants_i from exchange data */
 		n=*(exchange->n_i);
@@ -1472,8 +1835,8 @@ int tersoff_mult_3bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,t_atom *ak,u8 bc) {
 
 		/* d_costheta */
 		tmp=1.0/dd;
-		d_costheta1=cos_theta/(d_ij*d_ij)-tmp;
-		d_costheta2=cos_theta/(d_ik*d_ik)-tmp;
+		d_costheta1=cos_theta/d_ij2-tmp;
+		d_costheta2=cos_theta/d_ik2-tmp;
 
 		/* some usefull values */
 		h_cos=(h-cos_theta);
@@ -1507,7 +1870,7 @@ int tersoff_mult_3bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,t_atom *ak,u8 bc) {
 			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));
+			df_c_ik=0.5*sin(arg)*(M_PI/(s_r*d_ik));
 
 			/* zeta_ij */
 			exchange->zeta_ij+=f_c_ik*g;
@@ -1525,27 +1888,32 @@ int tersoff_mult_3bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,t_atom *ak,u8 bc) {
 	/* 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);
+	d_jk2=v3_absolute_square(&dist_jk);
 
 	/* jk constants */
-	num=aj->bnum;
-	if(num==ak->bnum) {
-		R=params->R[num];
-		S=params->S[num];
-		B=params->B[num];
-		mu=params->mu[num];
+	brand=aj->brand;
+	if(brand==ak->brand) {
+		R=params->R[brand];
+		S=params->S[brand];
+		S2=params->S2[brand];
+		B=params->B[brand];
+		mu=params->mu[brand];
 		chi=1.0;
 	}
 	else {
 		R=params->Rmixed;
 		S=params->Smixed;
+		S2=params->S2mixed;
 		B=params->Bmixed;
 		mu=params->mu_m;
 		chi=params->chi;
 	}
 
 	/* zeta_ji/dzeta_ji contribution only for d_jk < S_jk */
-	if(d_jk<S) {
+	if(d_jk2<S2) {
+
+		/* now we need d_ik */
+		d_jk=sqrt(d_jk2);
 
 		/* constants_j from exchange data */
 		n=*(exchange->n_j);
@@ -1557,13 +1925,13 @@ int tersoff_mult_3bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,t_atom *ak,u8 bc) {
 		c2d2=exchange->cj2dj2;
 
 		/* cosine of theta_jik by scalaproduct */
-		rr=v3_scalar_product(&dist_ij,&dist_jk); /* times -1 */
+		rr=-v3_scalar_product(&dist_ij,&dist_jk); /* -1, as ij -> ji */
 		dd=d_ij*d_jk;
 		cos_theta=rr/dd;
 
 		/* d_costheta */
-		d_costheta1=1.0/(d_jk*d_ij);
-		d_costheta2=cos_theta/(d_ij*d_ij); /* in fact -cos(), but ^ */
+		d_costheta1=1.0/dd;
+		d_costheta2=cos_theta/d_ij2;
 
 		/* some usefull values */
 		h_cos=(h-cos_theta);
@@ -1573,12 +1941,16 @@ int tersoff_mult_3bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,t_atom *ak,u8 bc) {
 		/* g(cos_theta) */
 		g=1.0+c2d2-frac;
 
-		/* d_costheta_ij and dg(cos_theta) - needed in any case! */
+		/* d_costheta_jik and dg(cos_theta) - needed in any case! */
 		v3_scale(&temp1,&dist_jk,d_costheta1);
 		v3_scale(&temp2,&dist_ij,-d_costheta2); /* ji -> ij => -1 */
-		v3_add(&temp1,&temp1,&temp2);
+		//v3_add(&temp1,&temp1,&temp2);
+		v3_sub(&temp1,&temp1,&temp2); /* there is a minus! */
 		v3_scale(&temp1,&temp1,-2.0*frac*h_cos/d2_h_cos2); /* dg */
 
+		/* store dg in temp2 and use it for dVjk later */
+		v3_copy(&temp2,&temp1);
+
 		/* f_c_jk + {d,}zeta contribution (df_c_jk = 0) */
 		dzeta=&(exchange->dzeta_ji);
 		if(d_jk<R) {
@@ -1600,7 +1972,7 @@ int tersoff_mult_3bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,t_atom *ak,u8 bc) {
 			/* zeta_ji */
 			exchange->zeta_ji+=f_c_jk*g;
 
-			/* dzeta_ij */
+			/* dzeta_ji */
 			v3_scale(&temp1,&temp1,f_c_jk);
 			v3_add(dzeta,dzeta,&temp1);
 		}
@@ -1608,20 +1980,46 @@ int tersoff_mult_3bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,t_atom *ak,u8 bc) {
 		/* dV_jk stuff | add force contribution on atom i immediately */
 		if(exchange->d_ij_between_rs) {
 			zeta=f_c*g;
-			v3_scale(&temp1,&temp1,f_c);
-			v3_scale(&temp2,&dist_ij,df_c);
-			v3_add(&temp1,&temp1,&temp2);
+			v3_scale(&temp1,&temp2,f_c);
+			v3_scale(&temp2,&dist_ij,df_c*g);
+			v3_add(&temp2,&temp2,&temp1); /* -> dzeta_jk in temp2 */
 		}
 		else {
 			zeta=g;
-			// dzeta_jk is simply dg, which is temp1
+			// dzeta_jk is simply dg, which is stored in temp2
 		}
 		/* betajnj * zeta_jk ^ nj-1 */
 		tmp=exchange->betajnj*pow(zeta,(n-1.0));
-		tmp=-chi/2.0*pow(1+tmp*zeta,-1.0/(2.0*n)-1)*tmp;
-		v3_scale(&temp1,&temp1,tmp*B*exp(-mu*d_jk)*f_c_jk*0.5);
-		v3_add(&(ai->f),&(ai->f),&temp1); /* -1 skipped in f_a calc ^ */
+		tmp=-chi/2.0*pow((1+tmp*zeta),(-1.0/(2.0*n)-1))*tmp;
+		v3_scale(&temp2,&temp2,tmp*B*exp(-mu*d_jk)*f_c_jk*0.5);
+		v3_add(&(ai->f),&(ai->f),&temp2); /* -1 skipped in f_a calc ^ */
 		                                  /* scaled with 0.5 ^ */
+
+		/* virial */
+		ai->virial.xx-=temp2.x*dist_jk.x;
+		ai->virial.yy-=temp2.y*dist_jk.y;
+		ai->virial.zz-=temp2.z*dist_jk.z;
+		ai->virial.xy-=temp2.x*dist_jk.y;
+		ai->virial.xz-=temp2.x*dist_jk.z;
+		ai->virial.yz-=temp2.y*dist_jk.z;
+
+#ifdef DEBUG
+if(ai==&(moldyn->atom[0])) {
+	printf("dVjk (3bp) contrib:\n");
+	printf("%f | %f\n",temp2.x,ai->f.x);
+	printf("%f | %f\n",temp2.y,ai->f.y);
+	printf("%f | %f\n",temp2.z,ai->f.z);
+}
+#endif
+#ifdef VDEBUG
+if(ai==&(moldyn->atom[0])) {
+	printf("dVjk (3bp) contrib:\n");
+	printf("%f | %f\n",temp2.x*dist_jk.x,ai->virial.xx);
+	printf("%f | %f\n",temp2.y*dist_jk.y,ai->virial.yy);
+	printf("%f | %f\n",temp2.z*dist_jk.z,ai->virial.zz);
+}
+#endif
+
 	}
 
 	return 0;
@@ -1637,14 +2035,38 @@ int moldyn_bc_check(t_moldyn *moldyn) {
 	t_atom *atom;
 	t_3dvec *dim;
 	int i;
+	double x;
+	u8 byte;
+	int j,k;
 
 	atom=moldyn->atom;
 	dim=&(moldyn->dim);
+	x=dim->x/2;
 
 	for(i=0;i<moldyn->count;i++) {
-		if(atom[i].r.x>=dim->x/2||-atom[i].r.x>dim->x/2)
+		if(atom[i].r.x>=dim->x/2||-atom[i].r.x>dim->x/2) {
 			printf("FATAL: atom %d: x: %.20f (%.20f)\n",
 			       i,atom[i].r.x,dim->x/2);
+			printf("diagnostic:\n");
+			printf("-----------\natom.r.x:\n");
+			for(j=0;j<8;j++) {
+				memcpy(&byte,(u8 *)(&(atom[i].r.x))+j,1);
+				for(k=0;k<8;k++)
+					printf("%d%c",
+					((byte)&(1<<k))?1:0,
+					(k==7)?'\n':'|');
+			}
+			printf("---------------\nx=dim.x/2:\n");
+			for(j=0;j<8;j++) {
+				memcpy(&byte,(u8 *)(&x)+j,1);
+				for(k=0;k<8;k++)
+					printf("%d%c",
+					((byte)&(1<<k))?1:0,
+					(k==7)?'\n':'|');
+			}
+			if(atom[i].r.x==x) printf("the same!\n");
+			else printf("different!\n");
+		}
 		if(atom[i].r.y>=dim->y/2||-atom[i].r.y>dim->y/2)
 			printf("FATAL: atom %d: y: %.20f (%.20f)\n",
 			       i,atom[i].r.y,dim->y/2);
@@ -1655,4 +2077,3 @@ int moldyn_bc_check(t_moldyn *moldyn) {
 
 	return 0;
 }
-