First principles investigations of Fe-based A3BX ceramics with high stiffness and damage tolerance

Abstract

To find high-stiffness and damage tolerant materials, Fe-based A3BX carbides and nitrides anti-perosvkites were studied by first principles calculations. Firstly, they are found to be stable in cubic structures through the formation energy, elastic Born stability criteria and phonon dispersion spectra. The GGA functional is applied in the geometry optimization and the lattice constants are 3.730 Å, 3.715 Å, 3.832 Å, 3.828 Å for Fe3AlC, Fe3AlN, Fe3SnC and Fe3SnN, respectively. The elastic properties reveal that the materials all have large elastic moduli, high sound velocities, Debye temperatures. Among them, carbides have superior stiffness and quasi-ductile properties, and they can be further improved by additional pressures. Preliminary analysis of the electronic properties indicate they are ferromagnetic and metallic compounds. The high melting temperatures(>2600 K) confirm their high-temperature applications. The lowest thermal conductivity of Fe3SnN may demonstrate its potential in efficient solid-state refrigeration. And Fe3SnC is proposed to be the damage tolerant material with good prospects. Under 10 GPa external pressure, it can possess a ductile structure with Young's modulus of 402.15 GPa and Bulk modulus of 280.25 GPa.