Electronic and elastic properties of brownmillerite

Abstract

The elastic and electronic properties of brownmillerite (Ca2AlFeO5), the fourth component in mass of Portland cement, have been determined using Density Functional Theory. The Young’s modulus obtained in this work (E = 169 ± 2 GPa) is much closer to the experimental value than all the previously reported classical calculations. The electronic structure has been analyzed by calculating the band structure, the density of states and the crystal orbital overlap population curves. Results show that there are anti-bonding bonds between the iron and oxygen atoms which may create instability in the structure. The presence of those anti-bonding bonds might explain the limitation of force-field simulations when modeling the elastic properties of brownmillerite. Such a limitation may be extended to other structures derived from perovskites that present anti-bonding states.