Phase Stability, Electronic Structure, Compressibility, Elastic and Optical Properties of a Newly Discovered Ti3SnC2: A First-Principle Study

The phase stability, electronic structure, compressibility, optical and elastic properties of two polymorphs of Ti3SnC2 were investigated using first-principle calculation. α-Ti3SnC2 is confirmed to be the preferred equilibrium phase under high pressure and high temperature. The electronic structure calculations reveal that the Ti and C atoms form a strong Ti1-C-Ti2-C-Ti1 covalent bond chain while the bonding between Ti1 and Sn is relatively weak. In the low frequency range from radio waves to visible light, Ti3SnC2 behaves similarly with TiC. This material exhibits anisotropic compressibility under hydrostatic pressure: it is more compressible along the c-direction than along a-direction, related to the different bond stiffness and bond angle changes under high pressure. The second-order elastic coefficients were calculated. For the α-phase, the bulk, B, shear, G, and Young's moduli, E, are calculated to be 169.4, 124, and 197.4 GPa, respectively. The low G/B ratio partially explains why Ti3SnC2 is relatively soft and damage tolerant.