Insights into nanomechanical behavior of ettringite: Simulations of nanoindentation based on molecular dynamics

JY Zhao and YH Zhang and CY Cui and BM Wang, MATERIALS TODAY COMMUNICATIONS, 43, 111637 (2025).

DOI: 10.1016/j.mtcomm.2025.111637

Nanoindentation assesses micro-mechanical properties through load- induced surface responses, and molecular dynamics (MD) simulations can explore atomic-scale mechanics, yet MD simulations of nanoindentation for ettringite remain unexplored. This paper presents MD simulations of ettringite nanoindentation, examining the effects of modeling and loading conditions on the outcomes and investigating the anisotropic nanomechanical properties of ettringite. The results indicate that indentation modulus values, derived from both peripheral constraints and three-layer models, could align with referenced experimental ranges. Larger indentation radii increase ettringite's indentation modulus, while excessively smaller radii, such as 8 & Aring;, can result in simulated values below experimental ranges. Increasing the loading rate and indentation depth in MD simulations results in a higher indentation modulus for ettringite, and the indentation modulus of ettringite from simulations could match referenced experimental values at loading rates of 100-400 m/s and indentation depth of 8-12 & Aring;. The initial relaxation of ettringite during nanoindentation mainly occurs in the first few thousand steps of the holding stage, with later steps having little effect on the indentation modulus. Indentation on different crystal planes of ettringite yields significant variations in atomic density distributions for various atom types and alterations in the radial distribution functions curves among different atom pairs, culminating in the anisotropic nanoindentation behavior of ettringite. Accounting for this anisotropy, the simulated indentation modulus, obtained with an indenter radius of 12 & Aring;, a loading rate of 200 m/s and an indentation depth of 10 & Aring;, closely matches the average referenced experimentally determined value for ettringite.

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