Microstructure and polyamorphism of amorphous SiO2 at 500 K and 0÷20 GPa were investigated by molecular dynamics simulation. The results indicate that in the studied pressure range, the network structure of amorphous SiO2 includes SiOx structure units (x = 4, 5, 6) and OSiy (y = 2, 3). | Polyamorphism of amorphous SiO2 under compression based on two state model