still full of bugs ...
[physik/posic.git] / moldyn.c
index aaab0de..d33de02 100644 (file)
--- a/moldyn.c
+++ b/moldyn.c
 
 #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;
@@ -227,33 +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;
-
-       if(type==FCC) count*=4;
+       new=a*b*c;
+       count=moldyn->count;
 
-       if(type==DIAMOND) count*=8;
+       /* how many atoms do we expect */
+       if(type==FCC) new*=4;
+       if(type==DIAMOND) new*=8;
 
-       moldyn->atom=malloc(count*sizeof(t_atom));
-       if(moldyn->atom==NULL) {
-               perror("malloc (atoms)");
+       /* allocate space for 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);
@@ -261,30 +269,114 @@ int create_lattice(t_moldyn *moldyn,u8 type,double lc,int element,double mass,
        }
 
        /* debug */
-       if(ret!=count) {
-               printf("ok, there is something wrong ...\n");
-               printf("calculated -> %d atoms\n",count);
-               printf("created -> %d atoms\n",ret);
+       if(ret!=new) {
+               printf("[moldyn] creating lattice failed\n");
+               printf("  amount of atoms\n");
+               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;
@@ -292,9 +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;
@@ -302,12 +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;
 }
@@ -367,6 +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;
@@ -385,11 +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 */
@@ -422,6 +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;
@@ -436,11 +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));
@@ -489,9 +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);
 
@@ -506,11 +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);
        
@@ -520,26 +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;
@@ -609,7 +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;
 }
@@ -621,23 +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;
 }
@@ -660,16 +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 */
@@ -706,12 +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 */
 
@@ -723,15 +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)) {
@@ -759,7 +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);
                        }
                }
@@ -770,8 +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");
@@ -786,7 +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;
 
@@ -797,18 +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);
 
@@ -816,7 +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);
        }
@@ -827,7 +1044,7 @@ moldyn_bc_check(moldyn);
 
 /*
  *
- * potentials & corresponding forces
+ * potentials & corresponding forces & virial routine
  * 
  */
 
@@ -837,10 +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;
@@ -852,12 +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]));
@@ -878,7 +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;
@@ -913,7 +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;
@@ -939,7 +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);
 
                                }
@@ -951,11 +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;
 }
@@ -964,16 +1226,16 @@ 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;
 
        dim=&(moldyn->dim);
 
-       x=0.5*dim->x;
-       y=0.5*dim->y;
-       z=0.5*dim->z;
+       x=dim->x/2;
+       y=dim->y/2;
+       z=dim->z/2;
 
        if(moldyn->status&MOLDYN_STAT_PBX) {
                if(a->x>=x) a->x-=dim->x;
@@ -1002,23 +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;
@@ -1038,6 +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 */
@@ -1046,16 +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;
@@ -1069,7 +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]);
@@ -1097,11 +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);
 
@@ -1110,15 +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;
@@ -1130,16 +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 */
@@ -1162,27 +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;
@@ -1191,17 +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;
@@ -1209,8 +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;
        }
 
@@ -1234,7 +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 */
@@ -1245,6 +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);
 
@@ -1314,7 +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);
        }
@@ -1336,6 +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);
 
@@ -1364,6 +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;
 }
 
@@ -1376,9 +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;
@@ -1389,7 +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);
@@ -1424,6 +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;
@@ -1438,21 +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);
@@ -1470,8 +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);
@@ -1505,7 +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;
@@ -1523,27 +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);
@@ -1555,13 +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);
@@ -1571,12 +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) {
@@ -1598,7 +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);
                }
@@ -1606,20 +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;
@@ -1635,22 +2035,45 @@ 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*1e10,dim->x/2*1e10);
+                              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*1e10,dim->y/2*1e10);
+                              i,atom[i].r.y,dim->y/2);
                if(atom[i].r.z>=dim->z/2||-atom[i].r.z>dim->z/2)
                        printf("FATAL: atom %d: z: %.20f (%.20f)\n",
-                              i,atom[i].r.z*1e10,dim->z/2*1e10);
+                              i,atom[i].r.z,dim->z/2);
        }
 
        return 0;
 }
-