anchor.diff:    shift = max(sigma_C, sigma_N)*2**(1./6.) + 0.25
     call walls_colloid_lj% init(epsilon(1:1,:), sigma(1:1,:), sigma_cut(1:1,:), shift)
   
  +  if (N_type) then
  +     sigma_sphere = sigma_N
  +  else
  +     sigma_sphere = sigma_C
  +  end if
  +
     allocate(mass(N_colloids))
     if (dimer) then
        mass(1) = rho * sigma_C**3 * 4 * 3.14159265/3
        mass(2) = rho * sigma_N**3 * 4 * 3.14159265/3
     else
  -     if (N_type) then
  -        mass = rho * sigma_N**3 * 4 * 3.14159265/3
  -     else
  -        mass = rho * sigma_C**3 * 4 * 3.14159265/3
  -     end if
  +     mass = rho * sigma_sphere**3 * 4 * 3.14159265/3
     end if
   
  -  if (N_type) then
  -     sigma_single = sigma_N
  -  else
  -     sigma_single = sigma_C
  -  end if
  +  
   
     call solvent% init(N,N_species, system_name='solvent')
   
  
positive.code:                  write(*,*) 'on_track', on_track
                end if
             else
                if (colloids% pos(1,1) > (bufferlength+sigma_single)) then
                   on_track = .false.
                   write(*,*) 'on_track', on_track
                end if
  
negative.code:   integer, parameter :: n_bins_conc = 90
    double precision :: conc_z_cyl(n_bins_conc)
  
    double precision :: sigma_N, sigma_C, max_cut,alpha,sigma_sphere
    double precision :: shift, total_energy
    double precision :: sigma(3,2), sigma_cut(3,2), epsilon(3,2)
    double precision,allocatable :: mass(:)
  