Molecular Dynamics Simulations Of The Interfacial Structures In ZrB₂/SiC Composite

The lattice constants, electronic properties, elastic constants, anisotropy and Debye temperature were calculated by the first principles total-energy pseudopotential methods based on density function theory. Moreover, we got the surface energy of typical surface of ZrB₂ andβ-SiC using molecular mechanics methods. Then, the nine typical models of interfacial configuration were constructed. Molecular dynamics were adopted to simulate the dynamic developing courses of interfacial configuration from the sintering to room temperature of ZrB₂/SiC composites. We also calculated the ideal work of adhesion and analyzed the bonding features of all nine different interfacial configurations.The results showed that the lattice parameters and electronic structure agreed well with experimental results and other literatures with different calculating methods. It was found that the bonding nature in ZrB₂ was a combination of ionic, covalent and metallic from its electronic structure. The hybridization of B₂p and Zr4d from different layers was the dominate contribution for the creation of psuedogap and generated some unique properties, e, g. the high melting point and good conductivity.Stiffness matrix with five independent elastic constants of hexagonal ZrB₂ was yielded by fitting the volume vs. total energy curve to the Birch-Murnaghan equation of state with the unit cell having a given strain pattern. The bulk, elastic and shear modulus of polycrystalline ZrB₂ were 238, 525 and 231GPa, respectively. Poisson's ratio was 0.13. All results agreed well with experimental data. The analysis of elastic behavior of ZrB₂ indicated that it was more isotropic than one would suppose from its crystal structure. The Debye temperature calculated from the elastic constants was 927K, little larger than 910K from experimental data.The surface energy of some typical surfaces of ZrB₂ andβ-SiC were obtained with molecular mechanics method. However, the values of ZrB₂ surfaces deeply fluctuated cause of coarse force field parameters and complex bonding features. Reversely, the differences of surface energy ofβ-SiC were quite small. The dynamic developing courses of all nine models with increasing of temperature were simulated by molecular dynamics method. The results illustrated that the structure stability, atom radius, electronegativity and atoms positions of atom layer constructing the interface configuration were the main factors determining the bonding nature of interface. The ideal work of adhesion demonstrated that, W_{ZrB2(0001)//β-SiC(001)}>W_{ZrB2(0001)//β-SiC(110)}>W_{ZrB2(1120)//β-SiC(001)} (W_{ZrB2(1120)//β-SiC(110)}), and the trend of the distortion ratio of interface was just reverse by virtue of the ideal work of adhesion determined both from average bonds strength and the relaxation of interface. Actually, there existed the simulated interface configuration with observation the HRTEM photographs from the recent literature.