First-principles calculation of electronic structure and microwave dielectric properties of Fe-doped o-Cr7C3

The electronic structure and microwave dielectric properties of Fe-doped o-Cr7C3 were studied theoretically based on first-principles calculations. The 3d, 4s and 4p orbits of Cr atoms in o-Cr7C3 are hybridised. The electrons of these orbits pair up with electrons of the non-equivalent sp3 hybrid orbits of C atoms into delocalisation electron-deficient covalent bonds, leading to the formation of a covalent bond net consisting of Cr–C–Cr chains in the metallic matrix. Fe-doping can substantially improve the microwave dielectric properties of o-Cr7C3. The microwave dielectric properties of Fe-doped o-Cr7C3 are closely related to the strength of covalent bonds and metallic anti-bonding. The electrons in the covalent bonds and metallic anti-bonding in the microwave field are apt to be polarised because the effect of the positive ions cores on the delocalised electrons is relatively weak. Precise knowledge of the electronic structure of Fe-doped o-Cr7C3 will facilitate better understanding of its microwave dielectric properties.