Mechanical anisotropy and ideal strength of ThBC

The mechanical and thermodynamic properties of ThBC were examined by first-principles calculations based on density functional theory. The equilibrium geometry, elastic stiffness constants, mechanical moduli, Poisson's ratio, elastic wave velocities, and Debye temperature of ThBC were systematically investigated. ThBC exhibits ductile characteristics. The directional Young's modulus E and bulk modulus B and several mechanical anisotropic factors show the mechanical anisotropic properties of ThBC. Under tensile strain, ThBC is easy to cleave along the [111] direction, with an ideal strength of 5.7 GPa. The fracture in ThBC under shear strain occurs along the [11¯0] direction of the (111) plane. Phonon calculations revealed the thermodynamic stability of ThBC, which is consistent with the experimental observation. The Helmholtz free energy, entropy, and heat capacity were obtained under the quasi-harmonic approximation.