Crystal Structure and Theoretical Elastic Property of a New Ternary Ceramic HfAl 4 C 4

HfAl 4 C 4 , a new ternary aluminum carbide, was discovered and its crystal structure was determined by a combination of X‐ray diffraction, transmission electron microscopy, and first‐principles calculations. The crystal structure is trigonal belonging to thespace group. The refined lattice constants are a =0.3308 nm, c =2.190 nm. First‐principles method was used to calculate the theoretical second‐order elastic constants, bulk modulus, shear modulus, and the Young's modulus of HfAl 4 C 4 . It shows that HfAl 4 C 4 has relatively high elastic stiffness.