Dynamic susceptibility of supercooled water and its relation to the dynamic crossover phenomenon

We study the dynamic susceptibility χT (Q,t) of deeply supercooled water by means of quasielastic neutron scattering and molecular dynamics simulations. Both techniques show an increase in the peak height of χT (Q,t) as the temperature is lowered toward the dynamic crossover temperature TL. Below TL, the peak height decreases steadily. We attribute this phenomenon to the change in slope of the Arrhenius plot of the translational relaxation time at TL. In contrast, the peak height of the calculated four-point correlation function χ4 (Q,t), directly related to the size of dynamic heterogeneity, increases toward and below TL.