Mercury Sulfide Dimorphism in Thioarsenate Glasses

Abstract

Crystalline mercury sulfide exists in two drastically different polymorphic forms in different domains of the P,T-diagram: red chain-like insulator α-HgS, stable below 344 °C, and black tetrahedral narrow-band semiconductor β-HgS, stable at higher temperatures. Using pulsed neutron and high-energy X-ray diffraction, we show that these two mercury bonding patterns are present simultaneously in mercury thioarsenate glasses HgS-As2S3. The population and interconnectivity of chain-like and tetrahedral dimorphous forms determine both the structural features and fundamental glass properties (thermal, electronic, etc.). DFT simulations of mercury species and RMC modeling of high-resolution diffraction data provide additional details on local Hg environment and connectivity implying the (HgS2/2)m oligomeric chains (1 ≤ m ≤ 6) are acting as a network former while the HgS4/4-related mixed agglomerated units behave as a modifier.

Bent HgI2 Molecules in the Melt and Sulfide Glasses: Implications for Nonlinear Optics

“…6(e-g), is related to glass fragmentation, also evidenced by a decrease of the glass transition temperatures from 471 K (x = 0) to 412 K (x = 0.2) 49 and observed in many metal chalcogenide and chalcohalide systems. [50][51][52][53] In contrast to molecular liquids, the FSDP in network glasses reflects mostly the ring statistics 54,55 and the FSDP amplitude correlates with population of rings. 43,56 Mercury (II) iodide additions are effectively destroying the intermediate range ordering in glassy As2S3 and transforming the continuous glass network into a patchwork of non-or weakly bonded structural fragments.…”

Ionic transport in AgI‐HgS‐As2S3 glasses: Critical percolation and modifier‐controlled domains

“…The critical temperature was also calculated from the activation energy data (Figure A) and the linear regression was consistent with Equation . The line slope value of −0.093(7) leads to a value of T 0 = 472(37) K. It is clear that the two methods give similar results and that the critical temperature T 0 , taking into account the large incertitude value of 37 K, is relatively close to the glass‐transition temperature for the glassy (HgS) 0.5 (As 2 S 3 ) 0.5 host matrix, 422 ± 5 K …”

“…The higher feature might be related to the concentration of the silver-related units near the mercury tetrahedral units HgS 4/4 rather than the twofold coordinated mercury HgS 2/2 units in the pseudobinary (HgS) 0.5 (As 2 S 3 ) 0.5 . 34,35 Thus, similar to other silverdoped chalcogenide systems, 26 one would not expect significant changes in the short-and intermediate-range order of the glassy matrix in the critical percolation domain, as the concentration of the added Ag + mobile ion is too small. The ionic conductivity in AgI-poor glasses of the studied pseudoternary system (x ≤ 0.1-0.2) is actually typical of the critical percolation.…”

“…The plot of T 0 vs. < n 0 > shows that the critical percolation regime for the studied (AgI) x (HgS) 0.5‐ x/2 (As 2 S 3 ) 0.5‐ x/2 glasses (this work) is, though slightly higher, comparable to its Ag + ion‐conducting counterparts (Figure ). The higher feature might be related to the concentration of the silver‐related units near the mercury tetrahedral units HgS 4/4 rather than the twofold coordinated mercury HgS 2/2 units in the pseudo‐binary (HgS) 0.5 (As 2 S 3 ) 0.5 . Thus, similar to other silver‐doped chalcogenide systems, one would not expect significant changes in the short‐ and intermediate‐range order of the glassy matrix in the critical percolation domain, as the concentration of the added Ag + mobile ion is too small.…”

“…The critical temperature was also calculated from the activation energy data (Figure 4A) and the linear regression was consistent with Equation (5). The line slope value of À0.093 (7) leads to a value of T 0 = 472(37) K. It is clear that the two methods give similar results and that the critical temperature T 0 , taking into account the large incertitude value of 37 K, is relatively close to the glass-transition temperature for the glassy (HgS) 0.5 (As 2 S 3 ) 0.5 host matrix, 422 AE 5 K. 34,35 The critical percolation model 24,25 emphasizes that the critical temperature, T 0 , is a primordial parameter to describe the percolation phenomena in glasses as it is related to the average coordination number <n 0 > of the host matrix via Equation (6):…”