Mechanical softening of thermoelectric semiconductor Mg_2Si from nanotwinning
Guodong Li, Qi An, Sergey I. Morozov, Bo Duan, William A. Goddard III, Pengcheng Zhai, Qingjie Zhang, G. Jeffrey Snyder
Abstract
Nanotwinning exhibits strengthening effects in many metals, semiconductors, and ceramics. However, we show from ab-initio calculations that nanotwins significantly decrease the strength of thermoelectric semiconductor Mg_2Si. The theoretical shear strength of nanotwinned Mg_2Si is found to be 0.93 GPa, much lower than that (6.88 GPa) of flawless Mg_2Si. Stretching the Mg-Si bond under deformation leads to the structural softening and failure of flawless Mg_2Si. While in nanotwinned Mg_2Si, the Mg-Si bond at the twin boundary (TB) is expanded to accommodate the structural misfit, weakening the TB rigidity and leading to the low ideal shear strength.
Group Members
Li, G., An, Q., Morozov, S. I., Duan, B., III, W. A. G., Zhai, P., Zhang, Q., & Snyder, G. J. (2018). Mechanical softening of thermoelectric semiconductor Mg_2Si from nanotwinning. *Scripta Materialia*, *157*, 90-94. https://doi.org/10.1016/j.scriptamat.2018.08.002