Prediction the structure, mechanical properties and melting point of D8m‐Mo5SiB2 and Cmcm‐Mo5SiB2

Mo5SiB2is an ideal candidate for high temperature material. Although the D8l‐Mo5SiB2has been published, the other phases and the related properties of Mo5SiB2are still unclear. Here, two possible Mo5SiB2phases (D8m‐Mo5SiB2andCmcm‐Mo5SiB2) are predicted by using the first principles method. The structural stability, mechanical properties, melting point and electronic structure of Mo5SiB2are studied. The results show that the D8m‐Mo5SiB2andCmcm‐Mo5SiB2are thermodynamically and dynamically stables. The calculated bulk elastic modulus, shear modulus and Young's modulus of theCmcm‐Mo5SiB2are close to D8l‐Mo5SiB2. In addition, the predictedCmcm‐Mo5SiB2has high melting point (2518.5°C) compared to the D8l‐Mo5SiB2and D8m‐Mo5SiB2. In particular, the predicted D8m‐Mo5SiB2exhibits better plasticity than the D8l‐Mo5SiB2. The calculated density of states and Mulliken overlap population shows that the D8m‐Mo5SiB2andCmcm‐Mo5SiB2all exhibit metallic behavior. The metallic behavior mainly depends on the electronic interaction between Mo atom and B atom near Fermi level. Furthermore, the bond length of Mo‐B bond in the D8m‐Mo5SiB2is longer than the other two structures, which may be the reason why the ductility of the former is better than the latter.