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Molecular dynamics simulations have been performed to study the fundamental thermodynamic and mechanical properties of single-crystalline skutterudite CoSb3 in the nanometric scale. The several interesting thermodynamic predictions, including linear thermal expansion coefficient, specific heat capacity, thermal conductivity, and temperature dependence of elastic constants, show excellent agreement with data available in the literature. The classic mechanical tests of uniaxial tension and compression are performed respectively at constant temperatures. The CoSb3 single-crystal exhibits nonlinear elastic response during the deformation process and the sustainable stress is very high, demonstrating its outstanding stability. An interesting phenomenon occurs at compression that the stress-strain curve undergoes a transition. The cause of the transition is an atomic reconstruction, which is observed and interpreted on the basis of interatomic interactions. Both of the failure patterns under tension and compression reveal brittleness of the material. The increasing of temperature would result in a linear degradation of the effective Young’s modulus and ultimate strength, but its effect on Poisson’s ratio is negligible. The results provide the groundwork for future studies of service behavior of the skutterudites-based thermoelectric devices.

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Force-field-(FF)-based molecular simulation is essential but challenging in the theoretical research of complex thermoelectric (TE) materials. As they are general and crucial in TE semiconductors, the structural natures of anharmonicity and anisotropy can help us understand the inherent relation between thermal and mechanical behavior, and therefore the reliability of FF studies can be assessed. In this paper, given prior knowledge of the structural, mechanical and thermal properties as well as the limitations and necessary approximations of the FF method, a feasible and detailed FF modeling scheme and simulation has been designed for Bi2Te3, which is a typical high-performance TE material. Using the complementary approach combining quasi-harmonic lattice and molecular dynamics, the obtained potential is systematically confirmed to be accurate and efficient for the prediction of anharmonic and anisotropic behavior in thermotics and mechanics over a wide temperature range compared with the present Bi2Te3 models. This reveals that the intrinsic anisotropy and anharmonicity can measure the asymmetry of crystal lattices and the interatomic force in the current state. In addition, the significant distinction of temperature-dependent anharmonic effects in different directions of Bi2Te3 stems from its layered hierarchical structure, in which weak van der Waals bonding will probably be the key structural factor in comprehensively improving performance for mass production and wearable application. This prior-knowledge-based FF study is also suggested as a bridge between the theoretical understanding of micro-mechanisms and the experimental measurement of TE material properties, leading to a general framework of molecular simulation for other complex energy materials.

Along the c axis of the crystal lattice, Bi 2 Te 3 has periodic quintuple layers ''-Te1-Bi-Te2-Bi-Te1-'' which are connected by Van der Waals bonding. The weak bonding between Te1-Te1 layers substantially affects the mechanical properties of Bi 2 Te 3 . In the work discussed in this paper, the molecular dynamics method was used to study the mechanical properties of cuboid single-crystal of bulk Bi 2 Te 3 under compressive loads. The emphasis was on the effects of the Van der Waals bonding on the deformation and failure mechanism. The molecular dynamics simulation results revealed that Van der Waals bonding has a dominant effect on the mechanism of deformation, and fundamentally determines the ultimate stress and fracture strain. Furthermore, the compressive load along the a and c axes lead to quite different failure behavior, which can be distinguished by their specific effects on the deformation of the Van der Waals bonding. However, only models with the load along the a axis dramatically demonstrate the effect of strain rate on the stress-strain curves, in accordance with the poor structural stability.

To find a suitable potential for the interatomic interactions in molecular dynamics (MD) simulations for the study of the mechanical properties of the nanostructured thermoelectric material CoSb 3 , the advantages and disadvantages of existing potentials for the material are first reviewed and discussed, and then an enhanced potential is proposed in which both bondstretching and bond-angle distortions are considered. The structural stability and elastic properties of the crystalline CoSb 3 model within the developed potential are validated at finite temperature using classic MD tests. Comparison of the mechanical behavior of bulk single-crystal CoSb 3 , including the stress-strain curve and configuration evolution under tension, shows that the enhanced potential exhibits better reliability than the other potentials. Finally, the significance of the potential and its possible further improvement for broader application are briefly discussed.

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This paper reports molecular dynamics simulations performed to study the mechanical properties of Zn 4 Sb 3 nanofilms. In the simulations, interatomic interactions are represented by an enhanced atomic potential, and the crystal structure is based on the core structure of b-Zn 4 Sb 3 . For tensile loading along the [0 1 0] direction, the stability of the crystal structure of the Zn 4 Sb 3 nanofilms is analyzed by the radial distribution function method, and the stress-strain relation of the nanofilms is obtained at room temperature. Our present work indicates that the mechanical properties of Zn 4 Sb 3 nanofilms are quite different from those of bulk Zn 4 Sb 3 due to the impact of surface atoms of the nanostructure. From the atomic configuration, Zn 4 Sb 3 nanofilms exhibit typical brittleness. The size effect and the strain-rate effect on the extension of Zn 4 Sb 3 nanofilms are discussed in detail. Lastly, the mechanical properties of nanofilms based on different Zn 4 Sb 3 crystal structure models are examined.