Symmetry determined medium range order (MRO) contributions to the first sharp diffraction peak (FSDP) in non‐crystalline oxide and chalcogenide glasses

Abstract

The first sharp diffraction peak (FSDP) in the structure factor, S(Q), obtained from X‐ray and neutron diffraction data, is a characteristic feature of oxide and chalcogenide glasses. This feature reflects intermediate, or medium range order (MRO), and is expressed in terms of two experimentally determined parameters, the position, Q1(Å−1), and the full‐width at half‐maximum (FWHM), ΔQ1(Å−1), of the FSDP peak. These parameters determine a correlation length R = 2π/Q1(Å−1) and a coherence length L = 2π/ΔQ1(Å−1) that result from symmetry‐determined contributions to the fundamental electronic structures of SiO2 and GeSe2. Narrow distributions of third neighbor SiO and GeSe pair correlation distances are forced by strongly correlated symmetries of Si and Ge d‐states connected through intervening O and Se atoms, as well as Se inter‐atom lone‐pair repulsions in GeSe2. The local bonding of threefold coordinated B‐atoms in B2O3 is planar rather than tetragonal and a similar O 2pπB 3dπ overlap is symmetry forbidden. Instead symmetry allowed O 2pπB 3pπ bonding interactions play the determining role in promoting second‐neighbor BO atom coupling through intervening O‐atoms, thereby extending the correlation length scale into the MRO regime.

Structural Signatures for Thermodynamic Stability in Vitreous Silica: Insight from Machine Learning and Molecular Dynamics Simulations

“…7c). However, for the most stable structures, the real space length associated with the FWHM (2π/FWHM=11.5-12.5 Å) [39,40] is approaching the cutoff used for computing the PDFs, i.e., half of the simulation box length (∼ 19.5 Å).…”

Quantification of gas-accessible microporosity in metal-organic framework glasses

“…Zn 2+ cations here), which are surrounded by interstitial voids. 72,73 As such, QFSDP could be regarded as a reciprocal space signature for the glass networks' porosity and density. The full width at half maximum of the FSDP (∆QFSDP) is inversely proportional to the real space coherence length over which the MRO (i.e.…”

“…the correlation) exists. 72,73 We fitted the FSDP of the five amorphous materials under study here to a pseudo-Voigt function to derive QFSDP and ∆QFSDP (see Supporting Information Section 7.1). QFSDP is identical for all solids found at about 1.11…”

Dissolution of iron oxide nanoparticles inside polymer nanocapsules

“…with q 1 being the position and Dq 1 the full-width at halfmaximum of the FSDP can be determined, giving information about characteristic atomic distances and cluster sizes of the material. 28…”