Molecular dynamics simulations of nanoindentation of monocrystalline germanium

Abstract

Three-dimensional molecular dynamics simulations using the Tersoff potential are conducted to investigate the nanoindentation process of monocrystalline germanium (Ge). It is found that a phase transformation from fourfold-coordinated diamond cubic phase (Ge-I) to sixfold-coordinated β-tin phase (Ge-II) occurs during the nanoindentation process. The simulation results suggest that a pressure-induced phase transformation instead of dislocation-assisted plasticity is the dominant deformation mechanism of monocrystalline Ge thin films during the nanoindentation process.

A molecular dynamics simulation of boundary lubrication: The effect of n-alkanes chain length and normal load

“…During contact, the majority of the asperity atoms lubricated with C8-alkanes experienced dry contact that has a maximum stress of 40 GPa. This high value of the atomic stress has also been observed by MD simulations of indentation [23,24], cracking [25] and bending [26].…”

Atomic-scale analysis of nanoindentation behavior of high-entropy alloy

“…The size of the HEA sample is 20.8 nm× 20.8 nm× 15.5 nm, and a radius of spherical indenter with above the center of the HEA sample is 5.0 nm. The HEA sample is composed of three kinds of atoms: boundary layer atoms, thermostat layer atoms and Newtonian layer atoms [Zhu and Fang, 2012;Kelchner et al, 1998;Li et al, 2016;Ma and Yang, 2003; Newtonian atoms Thermostat atoms Boundary atoms Qiu et al, 2014;Fang et al, 2003]. As shown in Fig.…”

“…The thermostat atoms with a thickness of 1.5 nm of HEA sample adjacent to the boundary atoms are kept at a constant temperature of 300 K by the velocity scaling method to imitate the heat dissipation during real indentation process. The rest of atoms are Newtonian atoms, whose motions obey classic Newton's second law [Zhu and Fang, 2012;Kelchner et al, 1998;Li et al, 2016]. Periodic boundary conditions are imposed in the x-and y-directions.…”

“…Here, the cutoff radius of the Morse potential used for the remaining atom interactions is chosen to be 9.0Å. A purely virtual spherical repulsive rigid indenter with a force potential between indenter and substrate atoms is used in the simulation [Zhu and Fang, 2012;Ma and Yang, 2003;Qiu et al, 2014]:…”

“…After a full relaxation, the indentation begins and the indenter moves along the z-direction. Atomic interactions in Fe-Ni-Cr, Al-Al and Cu-Cu are modeled by the embedded atom method (EAM) potential [Zhu and Fang, 2012;Kelchner et al, 1998;Li et al, 2016;Ma and Yang, 2003;Qiu et al, 2014;Fang et al, 2003;Gannepalli and Mallapragada, 2001;Lai et al, 2013;Walsh et al, 2003;Goel et al, 2015], which is a multi-body potential energy function in the following form:…”