In this work, we present the results of large scale computer simulations using different approaches ranging from the usual quench from the melt to the building blocks method. We also present structural models of binary chalcogenide glasses, GeSe4, GeSe9, GeSe1.5, GeSe2 and SiSe2, amorphous silica and models of Ge-Se glasses heavily doped with Ag ((GeSe3)0.90Ag0.10, (GeSe3)0.85Ag0.15) through ab initio molecular dynamics simulations. GeSe4 and GeSe9 models are in good agreement with all the structural properties, vibrational properties and electronic density of states. The defect sites causing localization of electronic eigenstates in the band gap region are characterized. A detailed analysis of the atomic structure of these glasses shows that the Ge-centered tetrahedra are the predominant coordination motifs in g-GeSe4 and that the structure of g-GeSe9 consists of Se-chain segments which are cross-linked by Ge(Se1/2)4 tetrahedra.
Having reliable models of (GeSe3)0.90Ag0.10 and (GeSe3)0.85Ag0.15, we study the dynamics of the network of these glasses with an emphasis on the Ag ions. We highlight the existence of trapping centers and explicitly illustrate the trapping and release process from thermal MD simulation. We show that first principles simulation is a powerful tool to reveal the motion of ions in glass. The models appear to be in excellent agreement with an array of experiments and should be useful for subsequent studies of these interesting materials.
For certain binary IV-VI glasses, especially silica, we show that decoration of bond-centered column VI atoms on tetrahedral amorphous networks leads with appropriate re-scaling and relaxation to highly realistic models of IV-VI binary glasses. The models obtained present some additional features such as a proper asymptotic behavior in S(Q) for large Q. The method is used to produce other models such as GeSe2 and SiSe2. We also show that the combination of a reverse Monte Carlo approach with approximate first-principles molecular dynamics is effective for a challenging material g-GeSe2.