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The lack of a reliable method to evaluate the convergence of molecular dynamics simulations has contributed to discrepancies in different areas of molecular dynamics. In the present work, the method of information entropy is introduced to molecular dynamics for stationarity assessment. The Shannon information entropy formalism is used to monitor the convergence of the atom motion to a steady state in a continuous spatial domain and is also used to assess the stationarity of calculated multidimensional fields such as the temperature field in a discrete spatial domain. It is demonstrated in this work that monitoring the information entropy of the atom position matrix provides a clear indicator of reaching steady state in radiation damage simulations, non-equilibrium molecular dynamics thermal conductivity computations, and simulations of Poiseuille and Couette flow in nanochannels. A main advantage of the present technique is that it is non-local and relies on fundamental quantities available in all molecular dynamics simulations. Unlike monitoring average temperature, the technique is applicable to simulations that conserve total energy such as reverse non-equilibrium molecular dynamics thermal conductivity computations and to simulations where energy dissipates through a boundary as in radiation damage simulations. The method is applied to simulations of iron using the Tersoff/ZBL splined potential, silicon using the Stillinger–Weber potential, and to Lennard–Jones fluid. Its applicability to both solids and fluids shows that the technique has potential for generalization to other areas in molecular dynamics. [ABSTRACT FROM AUTHOR]

Previous approaches to measure the through-thickness Young's modulus of a composite laminate often employed complicated specimens and test procedures, so very few through-thickness Young's moduli were reported. An efficient spherical nanoindentation approach was developed to measure the through-thickness Young's moduli of a woven fibric glass-fiber composite laminate. In this paper, the same approach is extended to the modulus measurement of four carbon fiber/epoxy IM7/937-7 laminates with complicated stacking sequences. The measured through-thickness Young's moduli were consistent with the transverse Young's modulus of the same composite system. Results show that the stacking sequences have little influence on the through-thickness Young's moduli, which could be explained by classical lamination theory for a thin composite laminate. [ABSTRACT FROM AUTHOR]

We investigate the collective effect of a high volume fraction of σ3 twin boundaries on the response of nanotwinned Cu to high dose He implantation near room temperature and find that they do not curtail the formation of vacancy and interstitial clusters. This result is rationalized through atomistic modeling, which shows that point defects at these boundaries have nearly identical properties to those in pure fcc Cu. [ABSTRACT FROM AUTHOR]

We report herein, for the first time, the effects of high-fluence (2×1017 ionscm−2; 14at.%) helium irradiation of polycrystalline Ti3AlC2 samples at 500°C. X-ray diffraction (XRD) confirmed that, despite swelling along the c-axis and shrinkage along the a-axis, the basic building blocks, viz. the Ti3C2 layers, remained intact after irradiation. The XRD results also suggest that He implantation disorders the Al layers. Despite the high dose at 500°C, He bubbles are present and are less than 1nm in diameter. This is an important finding if this material is to be used in light water or other fission reactors in the future. [ABSTRACT FROM AUTHOR]