Generation of Amorphous Silicon Dioxide Structures via Melting-Quenching Density Functional Modeling

Abstract

Ab initio quantum molecular dynamics simulation is used to transform a silicon dioxide crystal into silica amorphous states. Two type of amorphous states are obtained from the melts stabilized at temperatures well above the crystal melting point. The first type of amorphous states are obtained from the melts stabilized at comparably low temperatures of $$3000$$ and $$4000$$ K. These states are characterized by a perfect structure similar to those of the initial crystal and vitreous silica glass without point defects. Completely different amorphous states are obtained from the high temperature melts of $$5000$$ and $$6000$$ K. Structures of these amorphous states are less regular and contain point defects of silicon dioxide such as over-coordinated fivefold silicon, threefold oxygen atoms and a new silica defect 2-Bridging Oxygen Center. The latter is detected in the model of amorphous silica for the first time and it is formed by two neighbouring $$SiO_{4}$$ -tetrahedra with two common oxygen vertexes. The amorphous silica models can be useful for description of amorphous silicon dioxide films obtained by high energy ion-beam deposition process where a fast local melting-quenching process should exist.