Nb-based double transition metal silicides MAX-phase: A first-principle study

To explore the structural rationality and potential applications of the hypothetical chemically ordered double transition metal silicides MAX-phase Nb2ZrSiC2 and Nb2TiSiC2, we used density functional theory to systematically study the crystal structure and related properties of them and compared with the case of Nb3SiC2. Through the calculations of elastic constant and phonon dispersive curves, the stability of these three ceramics were investigated. Results show they are stable in mechanics and lattice dynamics. Then, normalized bond lengths as function of pressure for these compounds were computed to discuss their bond stiffness. In addition, the calculations of the densities of states for them indicate that they are all metallic-like conductors. And then, the calculations of dielectric function and reflectivity for these ceramics were performed to explore their optical properties. The good reflectivity performance in the infrared and close infrared region means they are potential coating materials on spacecraft in the future. At the end of this work, the Debye temperatures of these three ceramics compounds were obtained by calculating their longitudinal, transverse and mean and velocities, and results indicate they all exhibit a relatively good high temperature resistance.

Automated summary

The study investigates the structural rationality and potential applications of three chemically ordered transition metal silicides using density functional theory. Results show that they exhibit stability in mechanics and lattice dynamics, metallic-like conductivity, and promising optical properties for potential spacecraft coating materials. Additionally, the compounds demonstrate relatively good high temperature resistance.