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The role of group III, IV elements in Nb4AC3 MAX phases (A=Al, Si, Ga, Ge) and the unusual anisotropic behavior of electronic and optical properties

Abstract

The Niobium based Nb4AlC3, Nb4SiC3, Nb4GeC3 and Nb4GaC3 were investigated by means of density functional theory. Together with the known Nb4AlC3, the role of group III, IV elements in Nb4AC3 (A= Al, Si, Ga, Ge) on various properties were systematically investigated, and particularly the bulk moduli, shear moduli, and Young’s moduli helped us to approach the ductility. All studied compounds were found to be mechanically stable, and they also exhibit the metallic nature that results from the Nb-4d states being dominant at the Fermi level. The typical 4d-2p hybridization leads to strong Nb-C covalent bonding and the relatively weaker 4d-3p (4p) hybridization between Nb and A is identified. The latter does perturb the performance of materials. By varying A elements in the compounds, the position and the width of p states as well as hybridizations are altered, which determines the covalency and the iconicity of the chemical bonds. A high density of states at the Fermi level and the nesting effects in the Fermi surface are identified in Nb4SiC3, and link to its unusual anisotropic behavior. Furthermore, Nb4GeC3 is predicted to be a very promising candidate solar heating barrier material. Overall, the present work gives insight to the role of A elements on the electronic structure and physical properties of Nb4AC3 compounds. The tendencies and rules established here will fertilize the design of functional ceramic materials with desirable properties.

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Publication details

The article was received on 03 Mar 2017, accepted on 12 May 2017 and first published on 12 May 2017


Article type: Paper
DOI: 10.1039/C7CP01375B
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    The role of group III, IV elements in Nb4AC3 MAX phases (A=Al, Si, Ga, Ge) and the unusual anisotropic behavior of electronic and optical properties

    Y. Fu, B. Wang, Y. Teng, X. Zhu, X. Feng, M. Yan, P. A. Korzhavyi and W. Sun, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP01375B

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