Fig. 3: Arrhenius plot of the relaxation times.
From: Supercooled water confined in a metal-organic framework
The figure shows data for confined and bulk water, plotted as relaxation time τ vs. inverse temperature T (times 1000). Confined-water data in MFU-4l-HCOO (where MFU stands for “Metal-Organic Framework Ulm-University”) for process 3 are shown by the closed circles. For comparison, the diamonds show data for water in MCM-41 (Mobil Composition of Matter No. 41) with 2.1 nm pore size28, taken from Cerveny et al.13. In addition, relaxation times for liquid58 and supercooled bulk water49 are included at high temperatures (upright and inverted triangles, respectively) and for bulk low-density liquid (LDL) water at low temperatures (crosses)60. The dash-dotted line is a critical law with Tc = 228 K, proposed for bulk water61. The solid line is a fit of the high-temperature (T > 175 K, i.e., 1000/T < 5.7 K−1) data of process 3 with the Vogel–Fulcher–Tammann (VFT) function (Eq. 1; parameters: TVF = 122 K, D = 11.3, τ0 = 6.2 × 10−15 s). The dashed line at lower temperatures represents an Arrhenius law with its energy barrier of 0.48 eV fixed to the same value as for the low-temperature data of water in MCM-41 (dotted line). The approximate extent of the non-man’s land is indicated by the double-arrow on top of the figure. The inset demonstrates that τ(T) of process 3 can be described by the VFT (above Tcr) and Arrhenius laws (below Tcr) using identical prefactors τ0, which can be read off at 1000/T = 0.
