Use of Molecular Dynamics Simulations to Study the Effects of Nanopores and Vacancies on the Mechanical Properties of Bi_2Te_3

摘要

The effects of nanopores and vacancies on the mechanical properties of Bi_2Te_3 have been studied. Cuboid single-crystal bulk Bi_2Te_3 with atoms removed was chosen for molecular dynamics simulations. The mechanisms of action of the two defects can be distinguished by their specific effects on the crystal structure of the bulk Bi_2Te_3. The mechanical properties of the nanoporous Bi_2Te_3 are affected by porosity (φ), surface-to-volume ratio (ρ), and minimum cross-section length (L_(min)). The elastic modulus remains unchanged at 52.86 GPa for constant porosity of 0.7% whereas the ultimate stress and fracture strain gradually decrease with growing ρ or decreasing L_(min). The lattice stability of Bi_2Te_3 gradually weakens as the proportion of vacancies increases; this leads to increasing potential energy and poorer mechanical properties of Bi_2Te_3. When the proportion of Bi vacancies is increased from 0% to 8%, the elastic modulus decreases from 57.17 GPa to 36.32 GPa, a reduction of 36.47%, the ultimate stress decreases from 6.40 GPa to 3.61 GPa, a reduction of 43.59%, and the fracture strain decreases from 22.4% to 13.8%, a reduction of 38.39%.