Ground state structures of tantalum tetraboride and triboride: an ab initio study.
Tantalum-boron compounds, which are potential candidates for superhard multifunctional materials, may possess multiple stoichiometries and structures under pressure. Using first-principle methods, ground-state TaB3 with the monoclinic C2/m space group and high-pressure TaB4 with the orthorhombic Amm2 space group have been found. They are more stable than the previously proposed structures. High-pressure boron-rich Amm2-TaB4 can be quenched to ambient pressure. The ground-state C2/m-TaB3 and high-pressure Amm2-TaB4 are two potential ultra-incompressible and hard materials with a calculated hardness of 17.02 GPa and 30.02 GPa at ambient pressure, respectively. Detailed electronic structure and chemical bonding analysis proved that the high hardness value of Amm2-TaB4 mainly stems from the strong covalent boron-boron bonds in graphene-like B layers as well as B-B bonds between layers.
State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun, 130012, People's Republic of China. cuitian@jlu.edu.cn.
Shuli
S
Wei
Da
D
Li
Yunzhou
Y
Lv
Zhao
Z
Liu
Chunhong
C
Xu
Fubo
F
Tian
Defang
D
Duan
Bingbing
B
Liu
Tian
T
Cui