X-Git-Url: https://hackdaworld.org/gitweb/?a=blobdiff_plain;f=moldyn.c;h=94d596e91878237cf41a127cd8aa947cbcd18997;hb=fb951c04e522e4637618bf622fc67194c2a7b15f;hp=faa6b7c3ea6354a7f1ab08a51cca462d567fd405;hpb=2d562a1946322ae5b70bdce180321f32adbeab62;p=physik%2Fposic.git

diff --git a/moldyn.c b/moldyn.c
index faa6b7c..94d596e 100644
--- a/moldyn.c
+++ b/moldyn.c
@@ -19,6 +19,8 @@
 
 int moldyn_init(t_moldyn *moldyn,int argc,char **argv) {
 
+	printf("[moldyn] init\n");
+
 	memset(moldyn,0,sizeof(t_moldyn));
 
 	rand_init(&(moldyn->random),NULL,1);
@@ -30,6 +32,7 @@ int moldyn_init(t_moldyn *moldyn,int argc,char **argv) {
 int moldyn_shutdown(t_moldyn *moldyn) {
 
 	printf("[moldyn] shutdown\n");
+
 	moldyn_log_shutdown(moldyn);
 	link_cell_shutdown(moldyn);
 	rand_close(&(moldyn->random));
@@ -40,12 +43,16 @@ int moldyn_shutdown(t_moldyn *moldyn) {
 
 int set_int_alg(t_moldyn *moldyn,u8 algo) {
 
+	printf("[moldyn] integration algorithm: ");
+
 	switch(algo) {
 		case MOLDYN_INTEGRATE_VERLET:
 			moldyn->integrate=velocity_verlet;
+			printf("velocity verlet\n");
 			break;
 		default:
 			printf("unknown integration algorithm: %02x\n",algo);
+			printf("unknown\n");
 			return -1;
 	}
 
@@ -56,6 +63,8 @@ int set_cutoff(t_moldyn *moldyn,double cutoff) {
 
 	moldyn->cutoff=cutoff;
 
+	printf("[moldyn] cutoff [A]: %f\n",moldyn->cutoff);
+
 	return 0;
 }
 
@@ -63,6 +72,8 @@ int set_temperature(t_moldyn *moldyn,double t_ref) {
 
 	moldyn->t_ref=t_ref;
 
+	printf("[moldyn] temperature: %f\n",moldyn->t_ref);
+
 	return 0;
 }
 
@@ -70,6 +81,8 @@ int set_pressure(t_moldyn *moldyn,double p_ref) {
 
 	moldyn->p_ref=p_ref;
 
+	printf("[moldyn] pressure: %f\n",moldyn->p_ref);
+
 	return 0;
 }
 
@@ -79,6 +92,18 @@ int set_pt_scale(t_moldyn *moldyn,u8 ptype,double ptc,u8 ttype,double ttc) {
 	moldyn->t_tc=ttc;
 	moldyn->p_tc=ptc;
 
+	printf("[moldyn] p/t scaling:\n");
+
+	printf("  p: %s",ptype?"yes":"no ");
+	if(ptype)
+		printf(" | type: %02x | factor: %f",ptype,ptc);
+	printf("\n");
+
+	printf("  t: %s",ttype?"yes":"no ");
+	if(ttype)
+		printf(" | type: %02x | factor: %f",ttype,ttc);
+	printf("\n");
+
 	return 0;
 }
 
@@ -96,12 +121,15 @@ int set_dim(t_moldyn *moldyn,double x,double y,double z,u8 visualize) {
 		moldyn->vis.dim.z=z;
 	}
 
+	moldyn->dv=0.0001*moldyn->volume;
+
 	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");
+	printf("  visualize simulation box: %s\n",visualize?"yes":"no");
+	printf("  delta volume (pressure calc): %f\n",moldyn->dv);
 
 	return 0;
 }
@@ -115,6 +143,8 @@ int set_nn_dist(t_moldyn *moldyn,double dist) {
 
 int set_pbc(t_moldyn *moldyn,u8 x,u8 y,u8 z) {
 
+	printf("[moldyn] periodic boundary conditions:\n");
+
 	if(x)
 		moldyn->status|=MOLDYN_STAT_PBX;
 
@@ -124,6 +154,10 @@ int set_pbc(t_moldyn *moldyn,u8 x,u8 y,u8 z) {
 	if(z)
 		moldyn->status|=MOLDYN_STAT_PBZ;
 
+	printf("  x: %s\n",x?"yes":"no");
+	printf("  y: %s\n",y?"yes":"no");
+	printf("  z: %s\n",z?"yes":"no");
+
 	return 0;
 }
 
@@ -171,6 +205,8 @@ int moldyn_set_log(t_moldyn *moldyn,u8 type,int timer) {
 	char filename[128];
 	int ret;
 
+	printf("[moldyn] set log: ");
+
 	switch(type) {
 		case LOG_TOTAL_ENERGY:
 			moldyn->ewrite=timer;
@@ -183,6 +219,7 @@ int moldyn_set_log(t_moldyn *moldyn,u8 type,int timer) {
 				return moldyn->efd;
 			}
 			dprintf(moldyn->efd,"# total energy log file\n");
+			printf("total energy (%d)\n",timer);
 			break;
 		case LOG_TOTAL_MOMENTUM:
 			moldyn->mwrite=timer;
@@ -195,9 +232,11 @@ int moldyn_set_log(t_moldyn *moldyn,u8 type,int timer) {
 				return moldyn->mfd;
 			}
 			dprintf(moldyn->efd,"# total momentum log file\n");
+			printf("total momentum (%d)\n",timer);
 			break;
 		case SAVE_STEP:
 			moldyn->swrite=timer;
+			printf("save file (%d)\n",timer);
 			break;
 		case VISUAL_STEP:
 			moldyn->vwrite=timer;
@@ -206,9 +245,10 @@ int moldyn_set_log(t_moldyn *moldyn,u8 type,int timer) {
 				printf("[moldyn] visual init failure\n");
 				return ret;
 			}
+			printf("visual file (%d)\n",timer);
 			break;
 		default:
-			printf("[moldyn] unknown log mechanism: %02x\n",type);
+			printf("unknown log type: %02x\n",type);
 			return -1;
 	}
 
@@ -242,6 +282,7 @@ int create_lattice(t_moldyn *moldyn,u8 type,double lc,int element,double mass,
 	count=moldyn->count;
 
 	/* how many atoms do we expect */
+	if(type==CUBIC) new*=1;
 	if(type==FCC) new*=4;
 	if(type==DIAMOND) new*=8;
 
@@ -257,6 +298,9 @@ int create_lattice(t_moldyn *moldyn,u8 type,double lc,int element,double mass,
 	v3_zero(&origin);
 
 	switch(type) {
+		case CUBIC:
+			ret=cubic_init(a,b,c,atom,&origin);
+			break;
 		case FCC:
 			ret=fcc_init(a,b,c,lc,atom,&origin);
 			break;
@@ -292,6 +336,15 @@ int create_lattice(t_moldyn *moldyn,u8 type,double lc,int element,double mass,
 	return ret;
 }
 
+/* cubic init */
+int cubic_init(int a,int b,int c,double lc,t_atom *atom,t_3dvec *origin) {
+
+	int count;
+	t_3dvec r
+
+HIER WEITER !
+}
+
 /* fcc lattice init */
 int fcc_init(int a,int b,int c,double lc,t_atom *atom,t_3dvec *origin) {
 
@@ -429,6 +482,8 @@ int thermal_init(t_moldyn *moldyn,u8 equi_init) {
 	atom=moldyn->atom;
 	random=&(moldyn->random);
 
+	printf("[moldyn] thermal init (equi init: %s)\n",equi_init?"yes":"no");
+
 	/* gaussian distribution of velocities */
 	v3_zero(&p_total);
 	for(i=0;i<moldyn->count;i++) {
@@ -460,6 +515,29 @@ 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;
+
+	double_ekin=0;
+	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;
@@ -478,10 +556,11 @@ 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;
 		}
 	}
+	e*=0.5;
 	if(count!=0) moldyn->t=e/(1.5*count*K_BOLTZMANN);
 	else return 0;	/* no atoms involved in scaling! */
 	
@@ -515,6 +594,153 @@ int scale_velocity(t_moldyn *moldyn,u8 equi_init) {
 	return 0;
 }
 
+double ideal_gas_law_pressure(t_moldyn *moldyn) {
+
+	double p;
+
+	p=moldyn->count*moldyn->t*K_BOLTZMANN/moldyn->volume;
+printf("temp = %f => ideal gas law pressure: %f\n",moldyn->t,p/ATM);
+
+	return p;
+}
+
+double pressure_calc(t_moldyn *moldyn) {
+
+	int i;
+	double p1,p;
+	double v,h;
+	t_virial *virial;
+
+	v=0.0;
+	for(i=0;i<moldyn->count;i++) {
+		virial=&(moldyn->atom[i].virial);
+		v+=(virial->xx+virial->yy+virial->zz);
+	}
+
+	h=moldyn->count*K_BOLTZMANN*moldyn->t;
+
+	p=(h-ONE_THIRD*v);
+	p/=moldyn->volume;
+
+	p1=(moldyn->count*K_BOLTZMANN*moldyn->t-ONE_THIRD*moldyn->vt1);
+	p1/=moldyn->volume;
+
+	printf("debug: vt1=%f v=%f nkt=%f\n",moldyn->vt1,v,h);
+
+	printf("compare pressures: %f %f %f\n",p1/ATM,p/ATM,h/moldyn->volume/ATM);
+
+	return moldyn->p;
+}	
+
+double thermodynamic_pressure_calc(t_moldyn *moldyn) {
+
+	t_3dvec dim,*tp;
+	double u,p;
+	double scale;
+	t_atom *store;
+
+	tp=&(moldyn->tp);
+	store=malloc(moldyn->count*sizeof(t_atom));
+	if(store==NULL) {
+		printf("[moldyn] allocating store mem failed\n");
+		return -1;
+	}
+
+	/* save unscaled potential energy + atom/dim configuration */
+	u=moldyn->energy;
+	memcpy(store,moldyn->atom,moldyn->count*sizeof(t_atom));
+	dim=moldyn->dim;
+
+	/* derivative with respect to x direction */
+	scale=1.0+moldyn->dv/(moldyn->dim.y*moldyn->dim.z);
+	scale_dim(moldyn,scale,TRUE,0,0);
+	scale_atoms(moldyn,scale,TRUE,0,0);
+	potential_force_calc(moldyn);
+	tp->x=(moldyn->energy-u)/moldyn->dv;
+	p=tp->x*tp->x;
+
+	/* restore atomic configuration + dim */
+	memcpy(moldyn->atom,store,moldyn->count*sizeof(t_atom));
+	moldyn->dim=dim;
+
+	/* derivative with respect to y direction */
+	scale=1.0+moldyn->dv/(moldyn->dim.x*moldyn->dim.z);
+	scale_dim(moldyn,scale,0,TRUE,0);
+	scale_atoms(moldyn,scale,0,TRUE,0);
+	potential_force_calc(moldyn);
+	tp->y=(moldyn->energy-u)/moldyn->dv;
+	p+=tp->y*tp->y;
+
+	/* restore atomic configuration + dim */
+	memcpy(moldyn->atom,store,moldyn->count*sizeof(t_atom));
+	moldyn->dim=dim;
+
+	/* derivative with respect to z direction */
+	scale=1.0+moldyn->dv/(moldyn->dim.x*moldyn->dim.y);
+	scale_dim(moldyn,scale,0,0,TRUE);
+	scale_atoms(moldyn,scale,0,0,TRUE);
+	potential_force_calc(moldyn);
+	tp->z=(moldyn->energy-u)/moldyn->dv;
+	p+=tp->z*tp->z;
+
+	/* restore atomic configuration + dim */
+	memcpy(moldyn->atom,store,moldyn->count*sizeof(t_atom));
+	moldyn->dim=dim;
+
+	printf("dU/dV komp addiert = %f\n",(tp->x+tp->y+tp->z)/ATM);
+
+	scale=1.0+pow(moldyn->dv/moldyn->volume,ONE_THIRD);
+
+	scale_dim(moldyn,scale,1,1,1);
+	scale_dim(moldyn,scale,1,1,1);
+	potential_force_calc(moldyn);
+
+	printf("dU/dV einfach = %f\n",(moldyn->energy-u)/moldyn->dv/ATM);
+
+	/* restore atomic configuration + dim */
+	memcpy(moldyn->atom,store,moldyn->count*sizeof(t_atom));
+	moldyn->dim=dim;
+
+	/* restore energy */
+	moldyn->energy=u;
+
+	return sqrt(p);
+}
+
+double get_pressure(t_moldyn *moldyn) {
+
+	return moldyn->p;
+
+}
+
+int scale_dim(t_moldyn *moldyn,double scale,u8 x,u8 y,u8 z) {
+
+	t_3dvec *dim;
+
+	dim=&(moldyn->dim);
+
+	if(x) dim->x*=scale;
+	if(y) dim->y*=scale;
+	if(z) dim->z*=scale;
+
+	return 0;
+}
+
+int scale_atoms(t_moldyn *moldyn,double scale,u8 x,u8 y,u8 z) {
+
+	int i;
+	t_3dvec *r;
+
+	for(i=0;i<moldyn->count;i++) {
+		r=&(moldyn->atom[i].r);
+		if(x) r->x*=scale;
+		if(y) r->y*=scale;
+		if(z) r->z*=scale;
+	}
+
+	return 0;
+}
+
 int scale_volume(t_moldyn *moldyn) {
 
 	t_atom *atom;
@@ -592,11 +818,6 @@ 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));
@@ -659,6 +880,9 @@ 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++)
@@ -797,10 +1021,14 @@ int moldyn_add_schedule(t_moldyn *moldyn,int runs,double tau) {
 	schedule->tau=ptr;
 	schedule->tau[count-1]=tau;
 
+	printf("[moldyn] schedule added:\n");
+	printf("  number: %d | runs: %d | tau: %f\n",count-1,runs,tau);
+	                               
+
 	return 0;
 }
 
-int moldyn_set_schedule_hook(t_moldyn *moldyn,void *hook,void *hook_params) {
+int moldyn_set_schedule_hook(t_moldyn *moldyn,set_hook hook,void *hook_params) {
 
 	moldyn->schedule.hook=hook;
 	moldyn->schedule.hook_params=hook_params;
@@ -863,6 +1091,9 @@ int moldyn_integrate(t_moldyn *moldyn) {
 	/* debugging, ignore */
 	moldyn->debug=0;
 
+	/* tell the world */
+	printf("[moldyn] integration start, go get a coffee ...\n");
+
 	/* executing the schedule */
 	for(sched->count=0;sched->count<sched->total_sched;sched->count++) {
 
@@ -884,12 +1115,15 @@ int moldyn_integrate(t_moldyn *moldyn) {
 		if(moldyn->pt_scale&(P_SCALE_BERENDSEN|P_SCALE_DIRECT))
 			scale_volume(moldyn);
 
+printf("-> %f\n",thermodynamic_pressure_calc(moldyn)/ATM);
+
 		/* check for log & visualization */
 		if(e) {
 			if(!(i%e))
+				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));
 		}
@@ -946,7 +1180,7 @@ 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;
 
@@ -957,14 +1191,15 @@ 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);
 	}
 
@@ -975,7 +1210,7 @@ int velocity_verlet(t_moldyn *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);
 	}
@@ -986,7 +1221,7 @@ int velocity_verlet(t_moldyn *moldyn) {
 
 /*
  *
- * potentials & corresponding forces
+ * potentials & corresponding forces & virial routine
  * 
  */
 
@@ -1010,25 +1245,33 @@ int potential_force_calc(t_moldyn *moldyn) {
 
 	/* reset energy */
 	moldyn->energy=0.0;
-	
-	/* get energy and force of every atom */
+
+	/* reset virial */
+	moldyn->vt1=0.0;
+
+	/* reset force, site energy and virial 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);
+		/* reset virial */
+		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;
-
+	
 		/* reset site energy */
 		itom[i].e=0.0;
 
+	}
+
+	/* get energy,force and virial of every atom */
+	for(i=0;i<count;i++) {
+
 		/* single particle potential/force */
 		if(itom[i].attr&ATOM_ATTR_1BP)
 			moldyn->func1b(moldyn,&(itom[i]));
@@ -1130,6 +1373,29 @@ int potential_force_calc(t_moldyn *moldyn) {
 #ifdef DEBUG
 printf("\n\n");
 #endif
+#ifdef VDEBUG
+printf("\n\n");
+#endif
+
+temperature_calc(moldyn);
+pressure_calc(moldyn);
+ideal_gas_law_pressure(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;
 }
@@ -1176,23 +1442,29 @@ 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;
@@ -1212,6 +1484,8 @@ 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 */
@@ -1220,16 +1494,20 @@ 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;
@@ -1376,6 +1654,7 @@ int tersoff_mult_2bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,u8 bc) {
 
 	/* save for use in 3bp */
 	exchange->d_ij=d_ij;
+	exchange->d_ij2=d_ij2;
 	exchange->dist_ij=dist_ij;
 
 	/* more constants */
@@ -1443,6 +1722,14 @@ if(ai==&(moldyn->atom[0])) {
 	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 ... */
@@ -1514,7 +1801,6 @@ 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);
 	}
@@ -1551,6 +1837,14 @@ if(ai==&(moldyn->atom[0])) {
 	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 */
@@ -1582,12 +1876,13 @@ if(ai==&(moldyn->atom[0])) {
 	v3_add(&(ai->f),&(ai->f),&force);
 
 	/* virial - plus sign, as dist_ij = - dist_ji - (really??) */
-	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;
+// 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])) {
@@ -1596,6 +1891,14 @@ if(ai==&(moldyn->atom[0])) {
 	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;
@@ -1610,9 +1913,9 @@ 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;
@@ -1658,6 +1961,7 @@ 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;
@@ -1672,21 +1976,26 @@ 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 */
 	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);
@@ -1704,8 +2013,8 @@ 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);
@@ -1757,13 +2066,14 @@ 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 */
 	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;
@@ -1771,13 +2081,17 @@ int tersoff_mult_3bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,t_atom *ak,u8 bc) {
 	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);
@@ -1795,7 +2109,7 @@ int tersoff_mult_3bp(t_moldyn *moldyn,t_atom *ai,t_atom *aj,t_atom *ak,u8 bc) {
 
 		/* d_costheta */
 		d_costheta1=1.0/dd;
-		d_costheta2=cos_theta/(d_ij*d_ij);
+		d_costheta2=cos_theta/d_ij2;
 
 		/* some usefull values */
 		h_cos=(h-cos_theta);
@@ -1805,10 +2119,11 @@ 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 */
@@ -1873,6 +2188,14 @@ if(ai==&(moldyn->atom[0])) {
 	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
 
 	}