anchor.diff:    double precision :: skin, co_max, so_max
     integer :: N_MD_steps, N_loop
     integer :: n_extra_sorting
  -  double precision :: kin_co
   
     double precision :: conc_z(400)
     double precision :: colloid_pos(3,2)
  
positive.code:   colloids% species(1) = 1
    colloids% species(2) = 2
    colloids% vel = 0
    
    call random_number(solvent% vel(:, :))
    solvent% vel = (solvent% vel - 0.5d0)*sqrt(12*T)
    solvent% vel = solvent% vel - spread(sum(solvent% vel, dim=2)/solvent% Nmax, 2, solvent% Nmax)
  
negative.code:   e2 = compute_force_n2(colloids, solvent_cells% edges, colloid_lj)
    solvent% force_old = solvent% force
    colloids% force_old = colloids% force
  
    write(*,*) 'Running for', N_loop, 'loops'
    call main%tic()
  