Structural properties of Ge-S amorphous networks in relationship with rigidity transitions: Anab initiomolecular dynamics study

Abstract

We investigate the amorphous Ge x S 100−x (with 10≤ x ≤40) system from ab initio simulations. Results show a very good agreement with experimental findings from diffraction and the topology of the obtained structural models is further analyzed and compared with the selenide analogue. Differences emerge however from a detailed Molecular Dynamics analysis showing the ring statistics and the homopolar defects to not evolve similarly. The findings are also connected to Rigidity theory which provides a topological approach to decoding the physics of network glasses, and effect of composition and temperature are analyzed.

Progress, Challenges, and Rewards in Probing Melt Dynamics, Configurational Entropy Change, and Topological Phases of Group V‐ and Group IV‐Based Multicomponent Sulfide Glasses

“…The strong peaks furthermore suggest that in such As‐ and Ge‐deficient compositions, the network is dominated by essentially heteropolar bonding. The calculated bond distances ( d AsS = d GeS = 2.46 Å for Ge 25 As 25 S 50 ) are somewhat higher than those determined from the work of Soyer‐Uzun et al, [ 85 ] who found from RMC and also from a combination of neutron and X‐ray diffraction [ 86 ] a distance of 2.25 Å for the main peak, similar to those obtained for the corresponding binaries GeS [ 87 ] (2.21 Å). Conversely, the homopolar distances of GeGe (2.47 Å, inset of Figure 9b) and AsAs (2.49 Å for Ge 21 As 21 S 52 ) which appear at large compositions are found to be in agreement with the results determined from the similar experimental methods (2.46–2.48 Å for the average Ge/AsGe/As bond distance [ 86,85 ] ).…”

Linking Melt Dynamics With Topological Phases and Molecular Structure of Sodium Phosphate Glasses From Calorimetry, Raman Scattering, and Infrared Reflectance

“…The correlation between melt dynamics and glass topological phases has been observed recently in the chalcogenides such as Ge-Se (Bhosle et al, 2012a,b) and Ge-S (Chakraborty et al, 2017). The present case of SPG is one of the first on a modified oxide where melt dynamics correlate with glass topological phases.…”

“…The central finding of the present work is the existence of a reversibility window in the 37.5(3)% < x < 46.0(2)% range of soda across which glass transitions become thermally reversing. The square-well-like (Chakravarty, 2003;Chen et al, 2008;Bhosle et al, 2012a,b;Gunasekera et al, 2013b;Chakraborty and Boolchand, 2014;Chakraborty et al, 2017) variation of the non-reversing heat flow H nr (x) in the indicated range is a direct evidence of the isostatically rigid IP formed in the present glasses. Micoulaut (Micoulaut, 2010;Mantisi et al, 2015) has shown that the enthalpy of relaxation at T g of a glass constitutes a measure of n c -3, i.e., departure of the glass network from isostaticity (n c = 3).…”

Tetrahedral Complexity in Amorphous Networks: A Possible Clue for the Unique Properties of Phase‐Change Materials

“…Colored curves represent experimental data from XRD or ND, whereas thin black curves are simulation results: [ 4 ] (, expt. [ 20 ] ), [ 23 ] (, expt. [ 21,51 ] ), [ 24 ] (, expt.…”

“…Equation () is then compared with scattering results [ 16 ] and with the results from chemical analogs of the form obtained either experimentally (X = O, S, Se [ 20–22 ] ) or theoretically. [ 4,23,24 ] The represented materials display rather different structures as is entirely based on corner‐sharing (CS) tetrahedra, whereas both and have a mixed topology made of both CS and edge‐sharing (ES) tetrahedral. [ 24 ] The structure of , albeit investigated from XRD, [ 16 ] appears to be still not fully elucidated, although reverse Monte Carlo (RMC) methods [ 16,25 ] have characterized the structure in more detail.…”