  Upon loading, atomic networks can feature delayed viscoplastic relaxation.
However, the effect of composition and structure on such a relaxation remains
poorly understood. Herein, relying on accelerated molecular dynamics
simulations and topological constraint theory, we investigate the relationship
between atomic topology and stress-induced relaxation, by taking the example of
creep deformations in calcium--silicate--hydrates, the binding phase of
concrete. Under constant shear stress, C--S--H is found to feature delayed
logarithmic shear deformations. We demonstrate that the propensity for
relaxation is minimum for isostatic atomic networks, which are characterized by
the simultaneous absence of floppy internal modes of relaxation and eigen
stress. This suggests that topological nano-engineering could lead to the
discovery of non-aging materials.
