241 research outputs found
Fracture Toughness of Silicate Glasses: Insights from Molecular Dynamics Simulations
Understanding, predicting and eventually improving the resistance to fracture
of silicate materials is of primary importance to design new glasses that would
be tougher, while retaining their transparency. However, the atomic mechanism
of the fracture in amorphous silicate materials is still a topic of debate. In
particular, there is some controversy about the existence of ductility at the
nano-scale during the crack propagation. Here, we present simulations of the
fracture of three archetypical silicate glasses using molecular dynamics. We
show that the methodology that is used provide realistic values of fracture
energy and toughness. In addition, the simulations clearly suggest that
silicate glasses can show different degrees of ductility, depending on their
composition.Comment: arXiv admin note: text overlap with arXiv:1410.291
Creep of Bulk C--S--H: Insights from Molecular Dynamics Simulations
Understanding the physical origin of creep in calcium--silicate--hydrate
(C--S--H) is of primary importance, both for fundamental and practical
interest. Here, we present a new method, based on molecular dynamics
simulation, allowing us to simulate the long-term visco-elastic deformations of
C--S--H. Under a given shear stress, C--S--H features a gradually increasing
shear strain, which follows a logarithmic law. The computed creep modulus is
found to be independent of the shear stress applied and is in excellent
agreement with nanoindentation measurements, as extrapolated to zero porosity
Stretched Exponential Relaxation of Glasses at Low Temperature
The question of whether glass continues to relax at low temperature is of
fundamental and practical interest. Here, we report a novel atomistic
simulation method allowing us to directly access the long-term dynamics of
glass relaxation at room temperature. We find that the potential energy
relaxation follows a stretched exponential decay, with a stretching exponent
, as predicted by Phillips' diffusion-trap model. Interestingly,
volume relaxation is also found. However, it is not correlated to the energy
relaxation, but is rather a manifestation of the mixed alkali effect
- …