  Oxide glasses with a network structure are omnipresent in daily life. Often,
they are regarded as isotropic materials; however, structural anisotropy can be
induced through processing in mechanical fields and leads to unique materials
properties. Unfortunately, due to the lack of local, atomic-scale analysis
methods, the microscopic mechanisms leading to anisotropy remained elusive.
Using novel analysis methods on glasses generated by molecular dynamics
simulations, this paper provides a microscopic understanding of topological
anisotropy in silica (SiO$_2$) glass under mechanical loads. The anisotropy
observed in silica glass originates from a preferred orientation of SiO$_4$
tetrahedra at both short- and medium-range levels that can be controlled via
the mode of mechanical loading. The findings elucidate the relation between the
deformation protocol and the resulting anisotropic structure of the silica
network (involving both persistent and transient effects), and thus provide
important insight for the design of oxide glasses with tailored materials
properties.
