Mechanical softening of thermoelectric semiconductor Mg2Si from nanotwinning
Morozov, Sergey I.
Goddard III, William A.
Snyder, G. Jeffrey
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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 Mg2Si. The theoretical shear strength of nanotwinned Mg2Si is found to be 0.93 GPa, much lower than that (6.88 GPa) of flawless Mg2Si. Stretching the MgSi bond under deformation leads to the structural softening and failure of flawless Mg2Si. While in nanotwinned Mg2Si, the MgSi 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.
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