Physical properties of aGeS2glass using approximateab initiomolecular dynamics

Electronic structure of amorphous germanium disulfide via density-functional molecular dynamics simulations

“…Our sample contains 258 particles, confined in a cubic cell of 19.21Å (the density corresponds thus to the experimental value of 2.75 g/cm 3 [22]. At this density the pressure of the system is fairly small (close to 0.3 GPa) and does not affect the structural and vibrational properties of glassy GeS 2 as shown in previous studies [11,23]). Periodic boundary conditions are applied in order to limit surface effects, and only the Γ point is used to sample the Brillouin zone ( k = 0).…”

Vibrational signature of broken chemical order in aGeS2glass: A molecular dynamics simulation

“…We report in Fig.1 the results obtained for pairs of the same nature: Ge-Ge and S-S. The peaks corresponding to second neighbour distances, at 3.64Å for S-S pairs, and at 2.91Å and 3.41Å for Ge-Ge pairs (depending of whether the intertetrahedral connections are edge or corner-sharing), have already been analyzed in our previous work on the small sample [8] (in addition to the g(r) for the Ge-S pairs that does not change significantly in the large sample). However in the 258-particle sample, we observe in both graphs a small peak at short distances (2.42Å for Ge-Ge pairs and 2.23Å for S-S pairs), corresponding to nearest-neighbour bonds.…”

“…However, the importance of charge transfers in chalcogenide glasses [7] such as GeS 2 requires the use of an ab-initio model which can be extremely costly in time if the size of the system is not relatively small. In a previous study we have investigated a glassy GeS 2 sample containing 96 particles [8], using a non self-consistent ab-initio code based on the Sankey-Niklewski scheme called FIREBALL [9]. The good agreement of the results with the available experimental data showed the excellent quality of this model for the study of chalcogenide systems.…”

“…We will see later that these modes arise from structural defects that are not present in the small sample (as seen previously [8]) but in order to analyze the VDOS and to determine the nature of the atomic displacements responsible of the vibrational modes, we first calculate the Phase Quotient [23], which is defined as:…”

Photo-induced phenomena in GeO2 glass

“…Common to all these glasses is that the normal-bonding structure consists of the tetrahedral units of Si(Ge)O(S)4/2. Nevertheless, in consistent with different bonding angles of Si(Ge)-O(S)-Si(Ge), the units in Si(Ge)O2 are connected in a corner-shared way, while GeS2 contains edge-shared connections [49], which can be regarded as 2-membered rings. On the other hand, Si(Ge)O2 are believed to contain small rings such as 3-and 4-membered [11,40], and as noted above, GeO2 may contain a little amount of GeO6/2 units [46].…”