Chemical bonding and electronic-structure in MAX phases as viewed by Xray spectroscopy and density functional theory

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Elsevier Science SA
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This is a critical review of MAX-phase carbides and nitrides from an electronic-structure and chemical bonding perspective. This large group of nanolaminated materials is of great scientific and technological interest and exhibit a combination of metallic and ceramic features. These properties are related to the special crystal structure and bonding characteristics with alternating strong M-C bonds in high-density MC slabs, and relatively weak M-A bonds between the slabs. Here, we review the trend and relationship between the chemical bonding, conductivity, elastic and magnetic properties of the MAX phases in comparison to the parent binary MX compounds with the underlying electronic structure probed by polarized X-ray spectroscopy. Spectroscopic studies constitute important tests of the results of state-of-the-art electronic structure density functional theory that is extensively discussed and are generally consistent. By replacing the elements on the M, A, or X-sites in the crystal structure, the corresponding changes in the conductivity, elasticity, magnetism and other materials properties makes it possible to tailor the characteristics of this class of materials by controlling the strengths of their chemical bonds.
© 2016 Elsevier B.V. All rights reserved We gratefully acknowledge all valuable discussions in the MAX phase community. Martin Magnuson acknowledges financial support from the Swedish Foundation for Strategic Research (SSF) (no. RMA11-0029) through the synergy grant FUNCASE and the Carl Trygger Foundation. Maurizio Mattesini acknowledges financial support by the Spanish Ministry of Economy and Competitiveness (CGL2013-41860-P), and by the BBVA Foundation (PR14 CMA10) under the “I convocatoria de Ayudas Fundación BBVA a Investigadores, Innovadores y Creadores Culturales”.
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