DFT insights into the electronic structure, mechanical behaviour, lattice dynamics and defect processes in the first Sc-based MAX phase Sc2SnC

The ceramic and metallic properties of the MAX phases make them attractive for numerous technological applications. The very recent experimental synthesis of the first scandium (Sc) based MAX phase Sc 2 SnC is an important addition to the MAX phase family as it further expands the diversity of physical characteristics of this family. Here we employ density functional theory (DFT) calculations to investigate the structural, electronic, mechanical, lattice dynamical properties of Sc 2 SnC including defect processes to compare with those of existing M 2 SnC phases. The calculated structural properties are in good agreement with the experimental values. The new phase Sc 2 SnC is structurally, mechanically and dynamically stable. Sc 2 SnC is metallic with a mixture of covalent and ionic character. The covalency of Sc 2 SnC including M 2 SnC is mostly controlled by the effective valence. Sc 2 SnC in M 2 SnC family ranks second in the scale of deformability, softness and machinability. The elastic anisotropy level in Sc 2 SnC is moderate compared to the other M 2 SnC phases. Like other members of the M 2 SnC family, Sc 2 SnC has the potential to be etched into 2D MXenes and has the potential to be a thermal barrier coating (TBC) material. The hardness and melting point of Sc 2 SnC, including M 2 SnC, follows the trend of bulk modulus.