Dynamic Susceptibility of Supercooled Water and its relation to the Dynamic Crossover Phenomenon

We study the dynamic susceptibility chi(T)(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 chi(T)(Q,t) as the temperature is lowered toward the dynamic crossover temperature T(L). Below T(L), the peak height decreases steadily. We attribute this phenomenon to the change in slope of the Arrhenius plot of the translational relaxation time at T(L). In contrast, the peak height of the calculated four-point correlation function chi(4)(Q,t), directly related to the size of dynamic heterogeneity, increases toward and below T(L).