Transition of mechanisms underlying the rate effects and its significance

On the wurtzite to tetragonal phase transformation in ZnO nanowires

“…The reactive potential was also abandoned since it deviates from the prediction of the density functional theory at 0 K. Finally, the ab initio based potential was chosen because it performs well on the following four aspects: (i) the lattice constants of wurtzite and tetragonal phases it generated are consistent with that of the density functional theory [14,33]; (ii) the thermal properties reconstructed echo with the experimental results and thus the temperature effect on phase transformation is detectable [33,44]; (iii) surface energy was also modeled and this allows investigation on the size-dependent mechanical properties of ZnO NWs [33]; and (iv) most importantly, phonon dispersion calculated converges to the experimental data [33,45]. This feature offers precision to study the strain rate effect on deformation behaviors of NWs since the strain rate has much to do with the motion of phonons [46,47].…”

“…Before applying equation (4) to predict the wurtzite to tetragonal transformation, it is noticed that the strain rate effect on mechanical behaviors results from the competition between two time scales. One is the external loading rate and the other is the frequency of thermal vibration of atoms in a material at a given temperature [46,47]. Here, we particularly claim that e  t and B in equation (4) represent the two opponents.…”

Strengthening in Metal/Graphene Composites: Capturing the Transition from Interface to Precipitate Hardening

“…Prior to indentation, all samples were relaxed by energy minimization and then with dynamics relaxation over 10 ps in an NPT ensemble. Though the high strain rate is inevitable in conventional MDs due to the intrinsic time scale of atomic vibrations, our previous studies have shown that MDs can provide an insightful understanding of basic dislocation–Gr interaction mechanisms in Cu/Gr and Fe/Gr composites. , To avoid thermal effects, the temperature was set as 0.1 K in all cases. An additional simulation at 300 K in Figure S1 of the Supporting Information shows the same dislocation–Gr interaction mechanisms as the simulation at 0.1 K, indicating that our findings are valid when thermal effects are considered.…”

“…Prior to indentation, all samples were relaxed by energy minimization and then with dynamics relaxation over 10 ps in an NPT ensemble. Though the high strain rate is inevitable in conventional MDs due to the intrinsic time scale of atomic vibrations, 33 our previous studies have shown that MDs can provide an insightful understanding of basic dislocation−Gr interaction mechanisms in Cu/Gr and Fe/Gr composites. 25,34 To avoid thermal effects, the temperature was set as 0.1 K in all cases.…”