材料期刊网

The crystal structure, electronic structure and chemical bonding of Ti4AlN3 have been investigated by ab initio pseudopotential calculations. The equilibrium lattice parameters, atomic positions in the unit cell and bond lengths have been obtained by minimizing the total energy. The differences between the calculated and measured lattice constants are generally less than 1%. The electronic structure of Ti4AlN3 shows a metallic-like character and the 3d states of Ti dominate its electronic conductivity. The chemical bonding in Ti4AlN3 is an anisotropic metallic-covalent-ionic character. Ti-I,II and N atoms form strong covalent ionic bond in the Ti-II-N-II-Ti-I-N-I-Ti-I-NII-TiII-Al unit chain, while the bonding between Tin and Al is relatively weak. The strong covalent and ionic bonding in Ti4AlN3 is responsible for its high modulus and strength, while the metallic bonding results in its metallic properties. This kind of anisotropic bonding character results in the anisotropic properties of Ti4AlN3.