anchor.diff:          total_energy = e1+e2+e_wall+colloids% mass(1)*sum(colloids% vel(:,1)**2) + sum(solvent% vel**2)/2
        end if
   
  -     write(17,*) colloids% pos + colloids% image * spread(solvent_cells% edges, dim=2, ncopies=colloids% Nmax), &
  -                 colloids% vel, total_energy 
  -                 
        call random_number(solvent_cells% origin)
        solvent_cells% origin = solvent_cells% origin - 1
   
  
positive.code:            fixed = .false.
          end if
       end if
       !if (.not. on_track) then
       !   if (modulo(i,20)==0) then
       !      call concentration_field_cylindrical
       !      write(18,*) conc_z_cyl, colloid_pos
       !    end if
       !end if 
       
    end do setup
  
  
negative.code:   solvent_io%species_info%time = N_loop*N_MD_steps*dt
    call solvent_io%init(hfile, 'solvent', solvent)
  
    if (dimer) then
       colloids% species(1) = 1
       colloids% species(2) = 2
  