X-ray Scattering and O–O Pair-Distribution Functions of Amorphous Ices

Abstract

The structure factor and oxygen–oxygen pair-distribution functions of amorphous ices at liquid nitrogen temperature (T = 77 K) have been derived from wide-angle X-ray scattering (WAXS) up to interatomic distances of r = 23 Å, where local structure differences between the amorphous ices can be seen for the entire range. The distances to the first coordination shell for low-, high-, and very-high-density amorphous ice (LDA, HDA, VHDA) were determined to be 2.75, 2.78, and 2.80 Å, respectively, with high accuracy due to measurements up to a large momentum transfer of 23 Å–1. Similarities in pair-distribution functions between LDA and supercooled water at 254.1 K, HDA and liquid water at 365.9 K, and VHDA and high-pressure liquid water were found up to around 8 Å, but beyond that at longer distances, the similarities were lost. In addition, the structure of the high-density amorphous ices was compared to high-pressure crystalline ices IV, IX , and XII, and conclusions were drawn about the local ordering.

Electron Beam-Induced Transformation in High-Density Amorphous Ices

“…This value obtained for LDA is consistent with the X-ray scattering data. 36 The position of the VHDA maximum instead differs from the literature. From X-ray scattering, we would expect the Q -position in VHDA to be around Q 1 VHDA = 2.3 Å –1 .…”

“…Figure 2 b (lower panel) shows the integrated intensity for four selected time frames including a fit obtained by Bayesian inference ( Supporting Information ). For comparison, I ( Q ) measured by X-ray scattering 36 is plotted on top of Figure 2 b. The first ED diffraction pattern (frame 0, blue) shows two rings positioned at distances d 1 = 2.95 Å and d 2 = 2.17 Å.…”

“…The angular integrated data (a) are fitted (b, bottom panel) and further analyzed by integration of the FSDP (c). Top panel in (b) shows X-ray diffraction data, reproduced from refs ( 21 ) and ( 36 ).…”

“…(c-bottom) Additional measurement with 62 images with an exposure of 1 s/frame. Top panel in (b) shows X-ray diffraction data, reproduced from refs ( 21 ) and ( 36 ).…”

The nano-structural inhomogeneity of dynamic hydrogen bond network of TIP4P/2005 water

“…The peak of the distribution narrows with cooling. Figure 1d experimental data 53 on the position and height of the peaks. Upon melting of crystalline ice, the smearing of pair length distribution is observed from an interval of 2.7 Å-2.8 Å to an interval of 2.5 Å-3.2 Å.…”