anchor.diff:  
     call solvent_colloid_lj% init(epsilon, sigma, sigma_cut)
   
  -  
  +  epsilon(1,1) = PTread_d(config, 'epsilon_C_C')
  +  epsilon(1,2) = PTread_d(config, 'epsilon_N_C')
  +  epsilon(2,1) = PTread_d(config, 'epsilon_N_C')
  +  epsilon(2,2) = PTread_d(config, 'epsilon_N_N')
   
     sigma(1,1) = 2*sigma_C
     sigma(1,2) = sigma_C + sigma_N
  
positive.code:   sigma(2,2) = 2*sigma_N
    sigma_cut = sigma*2**(1.d0/6.d0)
  
    
  
    call colloid_lj% init(epsilon, sigma, sigma_cut)
  
    mass(1) = rho * sigma_C**3 * 4 * 3.14159265/3
  
negative.code: 
       call simple_mpcd_step(solvent, solvent_cells, mt)
  
       kin_co = (colloids% mass(1)*sum(colloids% vel(:,1)**2)+ colloids% mass(2)*sum(colloids% vel(:,2)**2))/2
       write(*,'(1i16,6f16.3,1e16.8)') i, e1, e2, &
            kin_co, sum(solvent% vel**2)/2, &
            e1+e2+kin_co+sum(solvent% vel**2)/2, &
  