This repository holds codes to perform the athermal quasistatic shearing (AQS) protocol. The protocol follows quasistatic dynamics, where a small shear is applied on the side of the simulation box, and the configuration is then minimized, to always maintain mechanical equilibrium.
The system of choice is an amorphous solid that has glassy-like dynamics and characteristics, taken originally from the work in [1]. The system is a polydisperse mixture of point-like particles enclosed in a square simulation box, making the simulation two-dimensional.
To equilibrate the system, the swapmc.jl code enables the fast equilibration
of the system by using the swap Monte Carlo technique, where the diameter
is swapped between particles. This is a non-physical rule, but it makes it
easier to equilibrate the system. One can choose the number of particles,
the reduced density and the reduced temperature.
The implementation of the AQS protocol is very standard. At every step,
the system is displaced by a small amount, and Lees-Edwards boundary conditions
are enforced, simulating a Couette flow. After displacing the particles, the
system is minimized to its closest energy minimum using the fast inertial
relaxation engine (FIRE) algorithm. This is the implementation in aqs.jl.
Alternatively, aqs_cg.jl implements a Polak-Ribiere conjugate gradient
minimization algorithm, using a line search that satisfies the Wolfe
conditions. However, the FIRE algorithm is preferred since it can reach
minima in less function calls than conjugate gradient.
- Ninarello, A. Models and Algorithms for the Next Generation of Glass Transition Studies. Phys. Rev. X 7, (2017).