In:
International Journal of Modern Physics B, World Scientific Pub Co Pte Ltd, Vol. 30, No. 20 ( 2016-08-10), p. 1650131-
Abstract:
The thermodynamic, mechanical and dynamic properties of TcB 3 and MoB 3 are systematically investigated at high-pressure by first-principles within density functional theory (DFT). The calculated formation enthalpies are negative for TcB 3 with considered structures under the pressure range from 0 to 100 GPa. Triboride hP4-TcB 3 (i.e., TcB 3 in hP4-OsB 3 type structure) has the lowest formation enthalpy of −1.44 eV under ambient condition. The largest shear modulus of 240 GPa and smallest Poisson’s ratio of 0.20 for oP16-TcB 3 are comparable to those of 267 GPa and 0.15 for ReB 2 . The calculated elastic constants show that MB 3 (M=Tc and Mo) are mechanically stable at ambient conditions, except for mP8-MoB 3 . The estimated high hardness of 33.4 and 33.1 GPa for oP16-TcB 3 and hP4-TcB 3 , respectively, are reported for the first time. The calculated lattice parameters for MoB 3 are in good agreement with the previously theoretical and experimental studies. Below 13 GPa, hP16-MoB 3 and hR24-MoB 3 are thermodynamically more favorable than MoB 3 in other structures. A pressure-induced phase transition is predicted at 13 GPa from hP16-MoB 3 and hR24-MoB 3 to hP4-MoB 3 . Above 13 GPa, hP4-MoB 3 becomes the thermodynamically most stable phase among MoB 3 in considered structures. All compounds with considered structures are metallic, and the electronic structures of MB 3 are governed by a strong hybridization between M-4d and B-2p states. The strong and directional covalent bonding between M-4d and B-2p as well as the strong interlayer interactions of boron layers are correlated to the high hardness of 38.0 and 38.4 GPa for hP16-MoB 3 and hR24-MoB 3 , respectively.
Type of Medium:
Online Resource
ISSN:
0217-9792
,
1793-6578
DOI:
10.1142/S0217979216501319
Language:
English
Publisher:
World Scientific Pub Co Pte Ltd
Publication Date:
2016
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