Internal Geometric and Electronic Structures of Natural Bornite Crystal

The geometric and electronic structures of bornite (Cu5FeS4) were studied using the first-principle calculation based on density function theory. By analyzing the results, a mixed bonding state is found in bornite, which is a strong covalent bond with much weaker ionic bonds. The interaction between S and Fe is stronger than that between S and Cu. The main bonding orbitals are as follows: Cu: 3d104s1, S: 3s23p4, and Fe: 3d64s2. Fe center is to be reduced receiving electrons in its 3d orbitals and the S center is mostly to be oxidized.