The melting curves and structural properties of tantalum (Ta) are investigated by molecular dynamics simulations combining with potential model developed by Ravelo et al. [Phys. Rev. B 88, 134101 (2013)]. Before calculations, five potentials are systematically compared with their abilities of producing reasonable compressional and equilibrium mechanical properties of Ta. We have improved the modified-Z method introduced by Wang et al. [J. Appl. Phys. 114, 163514 (2013)] by increasing the sizes in L x and L y of the rectangular parallelepiped box (L x ¼ L y (L z). The influences of size and aspect ratio of the simulation box to melting curves are also fully tested. The structural differences between solid and liquid are detected by number density and local-order parameters Q 6. Moreover, the atoms' diffusion with simulation time, defects, and vacancies formations in the sample are all studied by comparing situations in solid, solid-liquid coexistence, and liquid state. V

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First-principles calculations are employed to investigate the structural and elastic properties, formation enthalpies and chemical bonding features as well as hardness values of chromium tetraboride [Formula: see text] with different structures. The lattice parameters, Poisson’s ratio and [Formula: see text] ratio are also derived. Our calculations indicate that the orthorhombic structure with Pnnm symmetry is the most energetically stable one for CrB4. Except for [Formula: see text] structure with imaginary frequencies, another six new structures are investigated through the full phonon dispersion calculations. Their mechanical and thermodynamic stabilities are also studied by calculating the elastic constants and formation enthalpies. Our calculations show that the thermodynamic stabilities of all these [Formula: see text] phases can be enhanced under high pressure. The large shear moduli, Young’s moduli and hardness values indicate that these [Formula: see text] phases are potential hard materials. Analyses of the densities of states (DOSs) and electron localization functions (ELFs) provide further understandings of the chemical and physical properties of these [Formula: see text] phases. It is observed that the large occupations and high strengths of the B–B covalent bonds are important for the stabilities, incompressibility and hardnesses of these [Formula: see text] phases.