I am doing atomistic simulations for studying crack propagation in metals. In the literature I have seen people applying a ramped viscous damping to a “skin” region few angstroms inside the box boundaries (for absorbing strain waves emitted from the crack tip). The sample is divided in to two regions inner and the skin region. The temperature (in the skin region) is slowly ramped from its value in the inner region (say 10K), to those (say 0K) at the outer boundary of the skin region.
I want to use fix viscous with a thermostat (fix temp/rescale or any other thermostat with fix nve) for applying ramped viscous boundary conditions. I am not sure how to do this in lammps. Any help will be deeply appreciated.