Chemical and Structural Variety in Sodium Thioarsenate Glasses Studied by Neutron Diffraction and Supported by First-Principles Simulations

Abstract

Sodium-conducting sulfide glasses are promising materials for the next generation of solid-state batteries. Deep insight into the glass structure is required to ensure a functional design and tailoring of vitreous alloys for energy applications. Using pulsed neutron diffraction supported by first-principles molecular dynamics, we show a structural diversity of Na2S–As2S3 sodium thioarsenate glasses, consisting of long corner-sharing (CS) pyramidal chains CS-(AsSS2/2) k , small As p S q rings (p + q ≤ 11), mixed corner- and edge-sharing oligomers, edge-sharing (ES) dimers ES-As2S4, and isolated (ISO) pyramids ISO-AsS3, entirely or partially connected by sodium species. Polysulfide S–S bridges and structural units with homopolar As–As bonds complete the glass structure, which is basically different from structural motifs predicted by the equilibrium phase diagram. In contrast to superionic silver and sodium sulfide glasses, characterized by a significant population of isolated sulfur species Siso (0.20 < Siso/Stot < 0.28), that is, sulfur connected to only mobile cations M+ with a usual M/Siso stoichiometry of 2, poorly conducting Na2S–As2S3 alloys exhibit a modest Siso fraction of 6.2%.

Unraveling the Atomic Structure of Bulk Binary Ga–Te Glasses with Surprising Nanotectonic Features for Phase-Change Memory Applications

“…The neutron diffraction data for metallic Ga 0.2 Te 0.8 were available only in a limited Q range from 1.7 to 9 Å –1 and represent a linear interpolation between Ga 0.14 Te 0.86 and Ga 0.28 Te 0.72 melts . As previously reported, ,, the used hybrid GGA/PBE0 functional has a clear advantage compared to GGA/PBE or GGA/PBEsol both for glasses and liquids, except associated heavy computational costs. Figure illustrates a distinct difference in the glass and liquid interference Q [ S X ( Q ) – 1] and pair-distribution g X ( r ) functions in direct comparison with experimental data.…”

Bulk Glassy GeTe2: A Missing Member of the Tetrahedral GeX2 Family and a Precursor for the Next Generation of Phase-Change Materials

“…Another possible complication includes a tetrahedral interconnected subnetwork in glassy GeTe 2 with intermediate-range ordering reminiscent of g-GeS 2 and g-GeSe 2 . However, metal doping, e.g., using silver or copper, leads to network depolymerization , and faster transformation processes in the amorphous state. Copper tellurogermanate Cu 2 GeTe 3 is an exciting example revealing new perspectives. , We should note that a significant population of triangular rings in Cu 2 GeTe 3 are also present in liquid GeTe 2 , Figure , revealing a resemblance in intermediate-range structures.…”

Glassy GaS: transparent and unusually rigid thin films for visible to mid-IR memory applications

“…The standard PBE 34 or PBEsol 35 exchange-correlation functionals overestimate interatomic distances in chalcogenides and pnictides, 78,79 also confirmed in our FPMD simulations. The use of hybrid functionals B3LYP 78 or PBE0 80 improves the agreement with experiment. Figure 6(a)…”