Modeling of skutterudite CoSb3 with molecular dynamics method

Skutterudite materials have generated considerable interest as new thermoelectric materials over the past few years. For binary skutterudite compound CoSb3 with complicated cubic crystal structure, Morse potential energy function is employed to describe atomic interactions to lay special emphasis on its mechanical properties. The parameters of Morse potential function between different species of atom pairs (Co-Co, Sb-Sb and Co-Sb) are individually determined based on known crystal structures and elastic properties from experiment or first principle calculation results. To test the accuracy of the obtained potential parameters, molecular dynamics simulation was first performed to inverse deduce and compare with preceding used values, and the results show excellent agreement. Moreover, the practicability and feasibility of the potential was verified. In terms of the obtained potential parameters, the virtual uniaxial tensile simulation was performed for single crystal CoSb3 with bulk model using the conventional molecular dynamics algorithm. The mechanical response and deformation behavior are carefully analyzed. In contrast to conventional bulk CoSb3, single crystal bulk CoSb3 exhibits much better mechanical performances. It undergoes elastic deformation before 10% strain, and achieves ultimate stress 13.3 GPa at the strain of 10.2%, subsequently sudden fracture occurs near the middle of the model, demonstrating typical brittleness.