Structure of AgGeS glasses determined by isotopic substitution neutron scattering and reverse Monte Carlo simulations

The structure of Ag-doped GeS3 glasses (0,15,20,25 at.% Ag) was investigated by diffraction techniques and extended X-ray absorption fine structure measurements. Structural models were obtained by fitting the experimental datasets simultaneously by the reverse Monte Carlo simulation technique. It is observed that Ge has mostly S neighbours in GeS3, but Ge-Ge bonds appear already at 15% Ag content. Sulphur has ~2 S/Ge neighbours over the whole concentration range, while the S-Ag coordination number increases with increasing Ag content. Ag-Ag pairs can already be found at 15%Ag. The Ag-S mean coordination number changes from 2.17±0.2 to 2.86±0.2 between 15% and 25% Ag content. Unlike As-S network in AsS2-25Ag glass, the Ge-S network is not fragmented upon Agdoping of GeS3 glass.

Section: Ges 3 -Ag Glassesmentioning

confidence: 93%

Silver environment and covalent network rearrangement in GeS₃–Ag glasses

Rátkai

Kaban

Wágner

et al. 2013

“…There have been a number of other similar studies using neutron total scattering with isotopic substitution. These include ([Ag,Cu] 2 Se) 0.25 (AsSe) 0.75 [144]; (Ag 2 S) x (GeS 2 ) 1−x , with x = 0.3, 0.4 and 0.5 [145,146]; (Li 2 S) 0.5 (SiS 2 ) 0.5 using N Li and 6 Li which have negative and positive neutron scattering lengths, respectively [147]; (Ag 2 Te) 0.5 (As 2 Te 3 ) 0.5 [148]; and (CuI) 0.6 (Sb 2 Se 3 ) 0.4 [149]. The initial work on (Ag 2 S) 0.5 (GeS 2 ) 0.5 [145] additionally used RMC modelling to generate three-dimensional models of the structure from ( N Ag 2 S) 0.5 (GeS 2 ) 0.5 and compared the results with those from the isotopically enriched samples.…”

Section: Amorphous Superionic Conductorsmentioning

confidence: 99%

Disordering phenomena in superionic conductors

Keen¹

2002

135

129

Superionic conductors are materials which exhibit exceptionally high ionic conductivity whilst in the solid state. The manner in which certain structures accommodate superionic conduction has preoccupied many scientists throughout the latter part of the last century, beginning with the early debate about the disordered structure of the superionic α-phase of silver iodide. In this review, the key methods that have been used to deduce structural disorder in superionic conductors are described, and the important results summarized. The review focuses on simple archetypal systems, since these have dominated the literature, concentrating on more recent work and including emerging methodologies for deducing structural disorder. In most cases, the interpretation of diffuse scattering, as observed in scattering measurements, has played a crucial role in the understanding of these highly disordered systems and this is considered in some detail.

“…They are among the best ionic conductors, but our understanding of the conduction mechanism is hampered by a lack of detailed knowledge of the structure. Studies of the alloy system (Ag 2 S) x (GeS 2 ) 1−x , which forms a glass in the range x = 0 − 0.55 and has its maximum conductivity at x = 0.55, include Raman spectroscopy [13], extended x-ray absorption fine structure (EXAFS) [14], xray absorption spectroscopy, small angle and anomalous wide angle x-ray scattering [15], and isotope-substitution neutron diffraction (ND) with and without reverse Monte Carlo analysis [16,17]. These measurements indicated that the basic framework comprises GeS 4 tetrahedra.…”

Section: Introductionmentioning

confidence: 99%

Structure of amorphous Ag/Ge/S alloys: experimentally constrained density functional study

Akola

Beuneu

Jones

et al. 2015

Density functional/molecular dynamics simulations have been performed to determine structural and other properties of amorphous Ag/Ge/S and Ge/S alloys. In the former, the calculations have been combined with experimental data (x-ray and neutron diffraction, extended x-ray absorption fine structure). Ag/Ge/As alloys have high ionic conductivity and are among the most promising candidates for future memristor technology. We find excellent agreement between the experimental results and large-scale (500 atoms) simulations in Ag/Ge/S, and we compare and contrast the structures of Ge/S and Ag/Ge/S. The calculated electronic structures, vibrational densities of states, ionic mobilities, and cavity distributions of the amorphous materials are discussed and compared with data on crystalline phases where available. The high mobility of Ag in solid state electrolyte applications is related to the presence of cavities and can occur via jumps to a neighbouring vacant site.