Molecular Dynamics Study Of The Effect Of Nanotwins On Thermal Conductivity And Mechanical Properties Of InSb

Thermoelectric materials can realize thermoelectric cooling and thermoelectric power generation,and have broad application prospects in the field of new energy.Indium antimonide(InSb)is one of the most promising N-type thermoelectric materials among III-V semiconductors.However,it has the following two disadvantages:(1)high lattice thermal conductivity,which leads to its thermoelectric conversion efficiency lower than that of current typical thermoelectric materials,(2)The mechanical properties are poor,which makes the material less stable under complex working conditions.Previous studies have shown that nanotwins can synergistically control the thermal conductivity and mechanical properties of materials.(1)Using the method of non-equilibrium molecular dynamics,the lattice thermal conductivity of nanotwinned InSb with different thicknesses and angles is systematically studied,and the temperature effect is discussed,revealing the influence of nanotwin on the lattice thermal conductivity of InSb.The results show that the nanotwinned structure can significantly reduce the lattice thermal conductivity of InSb.When the nanotwin spacing is 1.1 nm,the lattice thermal conductivity of the nanotwinned InSb is 12.5 W/m K,which is 22.8% lower than that of the defect-free single crystal(16.2 W/m K).When the nanotwin are parallel to the heat flow direction,the lattice thermal conductivity of the InSb is 13.5 W/m K,and when the nanotwin are perpendicular to the heat flow direction,the lattice thermal conductivity of the InSb is12.6 W/m K,which are lower than those of the single crystal 16.7% and 22.2%,respectively.It is found that there is a temperature abrupt change at the nanotwin,which leads to a decrease in the temperature gradient and a significant decrease in the lattice thermal conductivity of InSb.At the same time,the lattice thermal conductivity of nanotwinned InSb can be quantitatively expressed by the nanotwin spacing and the lattice thermal conductivity of single crystal InSb.The closer the angle between nanotwin and heat flow is to 90°,the more obvious the effect of nanotwin on reducing the lattice thermal conductivity of the InSb.When the temperature increases from 300 K to 500 K,the lattice thermal conductivity of InSb without twins decreases by 19%.The thermal conductivity of InSb crystal lattice with nanotwin thickness of 50 nm decreases by 29%.The thermal conductivity of InSb lattice with 75 nm nanotwin thickness decreased by 27%.The higher the temperature,the more obvious the effect of nanotwinned structure on the lattice thermal conductivity of InSb.(2)The effects of different nanotwin spacings,angles and different temperatures on the shear and tensile mechanical properties of InSb thermoelectric materials were investigated,and their microscopic failure mechanisms were elucidated,respectively.The results show that changing the nanotwin spacing does not affect the shear and tensile mechanical properties of the InSb,because the change in the nanotwin spacing does not change the microscopic failure mechanism of the InSb under shear and tensile loads.The nanotwin spacing is fixed at 6.6 nm,when the angle between the nanotwins and the loading direction increases from 13.26° to 90°,it is found that the ultimate tensile strength of the nanotwinned InSb remains unchanged,and the ultimate shear strength first increases and then decreases,the model with an angle of 43.31° has the highest shear strength,shear modulus and fracture toughness.It is found that the change of angle between the nanotwin and the loading direction leads to the change of the initiation dislocation of the InSb before failure,so that the nanotwinned InSb with different angles has different failure modes.At the same time,the variation of nanotwin angle also leads to different shear stress of the same dislocation plane,so that the models with the same initiation dislocation have different ultimate strengths.The higher the temperature,the lower the strength of InSb,but the temperature did not change the microstructure evolution and failure mechanism of nanotwinned InSb under the action of the stress field.