It could also be employed to study the influence of indenter shape, temperature, or other processing conditions on material deformation expediently [7–11]. Almost the same experimental methods were used to investigate the phase transformation of monocrystalline germanium in nanoindentation, and metallic β-tin phase (Ge-II) was detected under Acadesine mw a certain pressure. It was found that the favored plastic deformation

of bulk crystalline germanium in nanoindentation was caused by shear-induced twinning aligned along the 111 planes and the dislocation slip [12, 13]. The explanation was that the initial plastic deformations were the twinning and dislocation slip. When the propagations of twinning and dislocation slip were blocked by increasing the load, the phase transformation started [12]. In the thin Ge film, the deformation process mentioned above was heavily influenced by the film thickness [14] and the velocity of loading [15]. At present, molecular dynamics simulation of nanoindentation

of germanium is rarely found except for Zhu and Fang’s study [16]. They proposed that a pressure-induced phase transformation was the dominant deformation SNS-032 cell line mechanism of the monocrystalline Ge film instead of dislocation-assisted plasticity. In this paper, the study is focused on the surface and subsurface deformation of monocrystalline germanium during nanoindentation on the (010), (110), and (111) crystal faces, respectively. The phase transformations are shown in detail at the atomic level, and the phase transformation path as well as the deformed layers after unloading on different crystal planes was analyzed. Methods Molecular dynamics simulation method The simulation model consists of a monocrystalline germanium workpiece and a spherical indenter. The workpiece has a size of 30 nm × 30 nm × 12 nm, including 748,461 germanium atoms. The germanium Roflumilast substrate includes three kinds of atoms: boundary atoms, thermostat atoms, and Newtonian atoms. The bottom outer layers of atoms in the substrate were fixed in space, and the layers neighboring them were kept at a constant temperature of 293 K to imitate heat

dissipation in a real nanoindentation condition. The rigid find more diamond indenter was designed as a spherical shape with a radius of 10 nm and moves at a velocity of 100 m/s during loading and unloading. The maximum penetration depth was set at 5 nm, where the indenter would remain for about 2,000 time steps. Nanoindentation simulations on three different crystallographically oriented surfaces including the (010), (101), and (111) planes were conducted. Since the Tersoff potential which considers the covalent bonds and the effect of bond angle has been used to deal with IV elements and those with a diamond lattice structure such as carbon, silicon, and germanium [16–18], and its great superiority has been shown, the interaction among the germanium atoms in this study adopts this potential.