anchor.diff:  
     call colloid_lj% init(epsilon, sigma_v, sigma_cut)
   
  +  ! no wall in x and z
  +  wall_sigma = -1
  +  wall_shift = 0
  +
  +  do_ywall = PTread_l(config, 'do_ywall', loc=params_group)
  +  if (do_ywall) then
  +     wall_sigma(2,:) = PTread_d(config, 'wall_sigma', loc=params_group)
  +     wall_shift(2) = PTread_d(config, 'wall_shift', loc=params_group)
  +     wall_epsilon = PTread_d(config, 'wall_epsilon', loc=params_group)
  +     call walls_colloid_lj% init(wall_epsilon, &
  +          wall_sigma, 3.d0**(1.d0/6.d0)*wall_sigma, wall_shift)
  +  end if
  +
     ! solvent index first, colloid index second, in solvent_colloid_lj
     sigma = PTread_d(config, 'sigma', loc=params_group)
     sigma_v = sigma
  
positive.code:   type(neighbor_list_t) :: neigh
    type(lj_params_t) :: solvent_colloid_lj
    type(lj_params_t) :: colloid_lj
  
    integer, parameter :: N_species = 2
  
  
negative.code:         v_com = v_com / tmp_mass
          kin_e = kin_e / 2
  
          call thermo_data%append(hfile, temperature, e1+e2+e3+e_wall, kin_e, e1+e2+e3+e_wall+kin_e, v_com)
          call axial_cf%add(i-equilibration_loops, com_pos, unit_r)
          call varia%tac()
       end if
  