anchor.diff:    colloids% pos(:,2) = solvent_cells% edges/2.0 
     colloids% pos(1,2) = colloids% pos(1,2) + d
     
  +  write(*, *) colloids% pos  
  +
     call solvent% random_placement(solvent_cells% edges, colloids, solvent_colloid_lj)
   
     call solvent% sort(solvent_cells)
  
positive.code: 
    call PTkill(config)
    
    open(15,file ='dimerdata_chemKapTEST.txt')
    
    write(*, *) colloids% pos
    colloids% species(1) = 1
    colloids% species(2) = 2
    colloids% vel = 0
  
negative.code:      call neigh% update_list(colloids, solvent, max_cut+skin, solvent_cells)
  
       call simple_mpcd_step(solvent, solvent_cells, mt)
       
       call refuel
       
       if (modulo(i,100)==0) then
          call concentration_field
          write(16,*) conc_z, colloid_pos
       end if
  
       kin_co = (colloids% mass(1)*sum(colloids% vel(:,1)**2)+ colloids% mass(2)*sum(colloids% vel(:,2)**2))/2
       write(*,'(1i16,6f16.3,1e16.8)') i, e1, e2, &
  