(a) The loss of Bragg peaks on initial compression indicates that the amorphization process is largely complete by ∼3 GPa. (b) The data quality on compression of the amorphous solid up to 7.2 GPa and subsequent complete decompression was sufficiently good for the calculation of G(r) using a Qmax of 19 Å−1. (c) The observed changes in S(Q) on decompression inside the DAC from 7.2 GPa are indicative of significant structural relaxation (the 7.2 GPa and decompressed curves have been offset vertically). (d) A comparison of the unsmoothed PDFs, G(r), computed from the highest pressure data and for the sample in the DAC before compression indicates that amorphization is associated with the loss of all well defined pair correlations above ∼4 Å.
A fit (top red line) to the ambient pressure experimental G(r) (top black line) for cubic ZrMo2O8, along with a difference curve and the partial pair distribution functions derived from the model. The data were recorded in a diamond anvil cell. G(r) was computed using Qmax = 19 Å−1 and the fit was undertaken using a model based on the P213 (orientationally ordered) α-ZrW2O8 structure.
A comparison of the smoothed pair correlation functions computed from the high pressure x-ray scattering data indicates systematic changes in both the M-O and M-O-M (M–Mo or Zr) links on compression and decompression. The smoothing was performed by computing a running average over the range 2π/Qmax around each point so as to suppress Fourier truncation ripples.
Differential PDFs, ΔG(r), computed from the high pressure G(r), clearly indicate that there are structural changes on both the densification and relaxation of the amorphous material. All of the above curves were computed by subtraction of the lowest pressure smoothed G(r) from the highest pressure smoothed G(r).
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