Crystal Structure and Mechanical Properties of ThBC₂

Abstract

Thorium borocarbide compounds have fascinating physical properties and diverse structures, and hence have stimulated great interest. In this work, we determine the ground state structure of ThBC2 by the unbiased structure prediction method based on first-principles calculations. The dynamical and elastic stabilities of our proposed ThBC2 are verified by the calculations of phonon spectrum and elastic constants. To study the mechanical properties fundamentally, we estimated the elastic anisotropy of ThBC2. The results show that the Young’s and shear moduli possess high degree of anisotropy. The ideal strength calculations reveal that ThBC2 readily collapses upon applied stress due to small ideal strengths. The cleavage fracture probably occurs along the [111] direction while slip may easily appear along the [ 1 ¯ 10 ] direction on the (111) plane for ThBC2. In addition, we provide an atomic explanation for the different characteristics of the strain−stress curves under different strains.

Keywords

• ThBC₂
• crystal structure
• anisotropic mechanical properties
• ideal strength
• first-principles calculations