Lattice dynamics, Raman and IR vibrations of stable Al/Si‐containing MAB phases: An ab initio and experimental study

Abstract

To comprehensively understand the physical properties of the MAB phases, a systematic exploration into their lattice dynamics, Raman, and infrared vibrations is undertaken for 24 previously screened stable Al/Si‐containing MAB phases with six crystal structures using density functional theory, where Raman experiments on Cr2AlB2 and Mo2AlB2 as well as the previous work confirm the high accuracy of these calculations with an error <5%. With a strong dependence on the atomic mass and chemical bonding, all Raman‐ and infrared‐active modes for these types are identified, including the atomic motion and wavenumbers. Unlike the 222 and 512 phases, the A atoms in the 212, 314, 414, and 416 phases do not participate in Raman vibrations. Moreover, a linear relationship is found between the Raman wavenumbers of the MAB phase and m−1/2, where m is the mass of primary vibrating atoms. Furthermore, the high coefficient of certainty (>0.90) underscores the robust explanatory power of m−1/2 for the vibrational wavenumber.