Using the critical diffusion coefficient shown in Figure 5.15, the amplitude D₀ can first be determined from the simple power law:

This gives D₀ = 2.69 × 10⁻⁹ m²/s.

Figure 5.15. Critical diffusion coefficient D_crit and total diffusion coefficient D_tot.

For the subsequent discussion based on mode-coupling theory, the relevant quantity is the total diffusion coefficient D_tot from Eq. (5.12). This expression includes the viscosity discussed in Section 5.3.1.1. According to [55], however, a crossover correction must be applied to the viscosity, thereby also affecting the diffusion coefficient.

Such a correction is intended to extend the description of critical systems to regions far from the critical point, where hydrodynamic effects rather than critical fluctuations must be considered. The corrected shear viscosity η_s is written as: