Density functional modeling of structural and electronic properties of amorphous high temperature oxides

• Published in: Journal of non-crystalline solids 2022-02, Vol.578, p.121170, Article 121170
• Main Authors: Sulimov, V.B., Kutov, D.C., Sulimov, A.V., Grigoriev, F.V., Tikhonravov, A.V.
• Format: Article
• Language: English
• Subjects: Ab initio molecular dynamics; Amorphous states; Density; Hafnia; Melting; Point defects; Quenching; Silica; Zirconia
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2021.121170

•Amorphous SiO2,ZrO2,HfO2 are obtained by DFT melt-quench for various melt T.•Melt threshold T is found for a given heat/cool rate separating types of structures.•Little known two edge sharing SiO4-tetrahedra are easily formed in some structures.•A sharp drop in density as a function of melt T is found for a-ZrO2 and a-HfO2.•The drop is a result of atom coordination numbers decrease in amorphous states. Ab initio molecular dynamics modeling in the NPT ensemble is used to obtain amorphous states by melting SiO2, ZrO2 and HfO2 crystals. A wide range of melt stabilization temperatures are used. Two types of SiO2 amorphous states are obtained. For melt temperatures below 4500 K, a perfect silica glass is obtained without any point defects. For melt temperatures above 4500 K, silica point defects such as threefold coordinated oxygen atoms, edge-sharing SiO4-tetrahedra, and others together with a wide range of Si-O-Si rings including 3-, and 4-membered rings appear. When the temperature of the melt exceeds the ZrO2 and HfO2 crystal melting point by 100 – 400 K, a sharp drop in the density of amorphous states is observed, accompanied by a decrease in atomic coordination, but this does not lead to the formation of defect states in the depth of the band gap of hafnium and zirconium dioxides.