First-principles calculations of the structural, mechanical, electronic and bonding properties of (CrB2)n CrAl with n = 1, 2, 3

• Published in: Journal of alloys and compounds Vol. 698; pp. 291 - 303
• Main Authors: Li, Xiaohong, Chagas da Silva, Maurício, Salahub, Dennis R.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 25.03.2017; Elsevier BV
• Subjects: (CrB2)nCrAl; Band crossing; Bonding strength; Chemical bonds; Chromium borides; Covalent bonds; Crystal structure; Density of states; Electric properties; Electronic structure; First-principles calculations; Hard materials; Mathematical models; Mechanical properties; Physical properties; Position (location); Principles; Quantum theory; Surface properties; Mechanical properties; First-principles calculations; Electronic structure; Band crossing; (CrB2)nCrAl
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2016.12.219

The crystal structure, the electronic structure and the mechanical properties were investigated for (CrB2)nCrAl with n = 1, 2, 3 by using the all-electron projector augmented wave method with the Perdew-Burke Ernzerhof functional. The calculated bulk moduli for Cr2AlB2, Cr3AlB4 and Cr4AlB6 were 202, 222 and 234 GPa, respectively, and the Young moduli were estimated to be 397, 412 and 434 GPa, respectively. All three materials were identified as stiff and hard materials; however, the density of states and the projected density of states analysis predicted a metallic behavior for all investigated materials. The partially filled d-orbitals of Cr atoms have an important role in attributing metallic behavior to these materials. The hardness of these materials was related to the presence of quite strong BB covalent bonds and the metallic characteristic arises from CrCr interactions. The chemical interpretation of the physical properties was made with the electron localization function and the investigation of the topology of the electron densities was provided, based on the quantum theory of atoms in molecules. Surface properties were explored for slab models, arbitrarily chosen to be along the a-axis. The metallic behavior of the compounds (CrB2)nCrAl continues in the surface model. Using the electron localization function and Bader's charge analysis, a small increase of the number of electronic carriers was observed, due to the localization of some AlAl bonds in the slab models. •Cr2AlB2, Cr3AlB4 and Cr4AlB6 crystals are considered metallic compounds.•Cr4AlB6 should have more electron carriers than Cr2AlB2 and Cr3AlB4.•A small increase of electronic carriers was observed for the slab models.•QTAIM analysis confirms the covalency of BB bonds, the ionicity of AlB bonds.