anchor.diff:       end do md
   
        write(15,*) colloids% pos + colloids% image * spread(solvent_cells% edges, dim=2, ncopies=colloids% Nmax), &
  -                 colloids% vel
  +                 colloids% vel, e1+e2+mass*sum(colloids% vel**2)/2+sum(solvent% vel**2)/2
   
        call solvent% sort(solvent_cells)
        call neigh% update_list(colloids, solvent, 1.5d0*sigma, solvent_cells)
  
positive.code:   write(*,*) '    i   |    e co so     |   e co co     |   kin co      |   kin so      |   total       |   temp        |'
    write(*,*) ''
  
    do i = 1, 500
       so_max = 0
       co_max = 0
       md: do j = 1, N_MD_steps
  
negative.code: 
    call neigh% update_list(colloids, solvent, 1.5d0*sigma, solvent_cells)
  
    tau = 0.1d0 !was 0.1d0 but we changed it to Kaprals' value(1.0) => doesn't work
    N_MD_steps = 100
    dt = tau / N_MD_steps
  
  