Nanotwin-induced ductile mechanism in thermoelectric semiconductor PbTe

M Huang and PC Zhai and GD Li and Q An and GD Li and WJ Li and QJ Zhang and WA Goddard, MATTER, 5 (2022).

DOI: 10.1016/j.matt.2022.03.010

Coherent twin boundaries (CTBs) with the lowest interfacial energy provide a strong phonon-CTB scattering source to suppress the lat-tice thermal conductivity needed for thermoelectric properties, but the impact on mechanical properties of PbTe remains unexplored. We construct nanotwinned structures with Pb- or Te-terminated CTB (Pb- or Te-CTB) along (111) plane and employ molecular dynamics simulations to examine structural evolution. We find that Pb-CTBs weaken ionic Pb-Te bonds to generate an easy dislocation source at CTBs. Due to nucleation and motion of partial dislocationson each Pb-CTB plane driven by shear load, Pb-CTBs gradually migrate to Te-CTBs, which is accompanied by breaking and re-forming of Pb-Te bonds. This ""catching bond'' maintains structural integrity while dramatically enhancing deformability of nanotwinned PbTe. Dislocations move from Te-CTBs toward twin lamellae, resulting in the structural slippage and fracture. These findings provide a theoretical strategy to improve the ductility of PbTe-based semiconductors through TB engineering.

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