  Indentation has been widely used for investigating the mechanical behavior of
glasses. However, how the various microscopic properties (such as atomic
structure and mechanics) of glass evolve from the immediate contact with the
indenter to the far-field regions, and how these observables are correlated to
each other remain largely unknown. Here, using large-scale molecular dynamics
simulations, we investigate the response of a prototypical sodium silicate
glass under shape contact load up to an indentation depth of 25 nm. Both the
short- and intermediate-range structures are found to exhibit notable changes
below the indent, indicating that indentation deformation induces a more
disordered and heterogeneous network structure. In addition, we find that the
indentation-induced changes of local properties all exhibit an exponential
decaying behavior with increasing distance from the indent. Comparison of the
characteristic decay lengths of these local properties indicates that the
structural origins of shear flow and densification are the changes of the
network modifier's coordination environment and the inter-tetrahedral
connection, respectively. The decay of densification is considerably slower
than that of shear strain, implying that the former might contribute more to
the deformation at the far-field regions. Our findings not only contribute to
an atomistic understanding of the indentation response of silicate glasses but
also pave the way towards rational design of damage-resistant glassy materials.
