First-principles investigation on chemical bonding and bulk modulus of the ternary carbide Zr2Al3C5

We have investigated the electronic structure, chemical bonding, and equations of state of Zr2Al3C5 by means of the ab initio pseudopotential total energy method. The chemical bonding displays layered characteristics and is similar to that of nanolaminate ternary aluminum carbides Ti2AlC and Ti3AlC2. Zr2Al3C5 could be fundamentally described as strong covalent bonding among Al-C-Zr-C-Zr-C-Al atomic chains being interleaved and mirrored by AlC2 blocks. The interplanar cohesion between covalent atomic chains and AlC2 blocks is very weak based on first-principles cohesion energy calculations. Inspired by the structure-property relationship of Ti2AlC and Ti3AlC2, it is expected that Zr2Al3C5 will have easy machinability, damage tolerance, and oxidation resistance besides the merits of refractory ZrC. Zr2Al3C5 has a theoretical bulk modulus of 160 GPa and illustrates elastic anisotropy under pressure below 20 GPa