A molecular dynamics study of nanoindentation of amorphous silicon carbide

Abstract

Through molecular dynamics simulation of nanoindentation of amorphous a-SiC, we have found a correlation between its atomic structure and the load-displacement ͑P-h͒ curve. We show that a density profile of a-SiC exhibits oscillations normal to the surface, analogous to liquid metal surfaces. Short-range P-h response of a-SiC is similar to that of crystalline 3C-SiC, e.g., it shows a series of load drops associated with local rearrangements of atoms. However, the load drops are less pronounced than in 3C-SiC due to lower critical stress required for rearrangement of local clusters of atoms. The nanoindentation damage is less localized than in 3C-SiC. The maximum pressure under the indenter is 60% lower than in 3C-SiC with the same system geometry. The onset of plastic deformation occurs at the depth of 0.5 Å, which is ϳ25% of the corresponding value in 3C-SiC. a-SiC exhibits lower damping as compared to 3C-SiC, which is reflected in the longer relaxation time of transient forces after each discrete indentation step.

Effect of the Spherical Indenter Tip Assumption on the Initial Plastic Yield Stress

“…1c. A molecular dynamics study showed that load drops are associated with local rearrangements of atoms (Szlufarska et al, 2007). …”

Generalized Langevin equation: An efficient approach to nonequilibrium molecular dynamics of open systems

“…In this new scheme, Eqs. (33) and (34) By appropriately choosing the frequency weight function Q(ω), one can simulate a GLE dynamics with a colored noise which is no longer proportional to the memory kernel.…”

“…In some instances [15,33,41], the equilibrium thermostats are applied to all atoms of the system in order to impose a specific temperature, while in other studies [7,[34][35][36][37][38][39][40], the Nosé [28], Hoover [30], or Berendsen [42] thermostats were used to thermostat only certain regions of the systems, although, strictly speaking, they were only proven to work if applied to the whole system (and additionally the Berendsen thermostat is not truly canonical). When these equilibrium thermostats are applied to nonequilibrium MD simulations, they introduce artifacts into the resulting trajectories in these simulations.…”

“…At the same time, these equilibrium thermostats are increasingly being applied to simulations studying nonequilibrium processes including tribology [33,34], energy dissipation [35], crack propagation [15], heat transport [7,[36][37][38][39][40], and irradiation [41]. In some instances [15,33,41], the equilibrium thermostats are applied to all atoms of the system in order to impose a specific temperature, while in other studies [7,[34][35][36][37][38][39][40], the Nosé [28], Hoover [30], or Berendsen [42] thermostats were used to thermostat only certain regions of the systems, although, strictly speaking, they were only proven to work if applied to the whole system (and additionally the Berendsen thermostat is not truly canonical).…”

Temperature control in molecular dynamic simulations of non-equilibrium processes

“…In the latter case, the chosen atoms would normally belong to several layers at the bottom of the substrate and the top of the upper sliding surface, next to the fixed layers served to mimic the missing bulk of the two surfaces. References [15,16,17,18,19,20,21] correspond to the first group, where we can see examples of velocity rescaling [17,18,19,21], Berendsen [15,20] and Nosé [16] thermostats used. The outer parts of the system (i.e.…”