Effect of Mo concentration on structural, mechanical, electronic and magnetic properties of Fe₂B: a first-principles study

ABSTRACT

First-principles calculations were performed to study the structural, mechanical, electronic and magnetic properties of Fe_(8−x)Mo_xB₄ (x = 0, 0.25, 0.5, 1, 2, 3, 4, 5, 6, 7, 8). Results show that the Mo atoms would enter the Fe₂B lattice by replacing the Fe atoms and cause a change in the crystal structure. According to the calculated formation enthalpy, all borides are thermodynamically stable; moreover, Mo would reduce the stability of Fe₂B when the Mo atomic number is less than four in the unit cell. On the whole, with the increase of Mo content, the Young’s moduli and shear moduli decrease firstly and then increase, while the bulk moduli get bigger. Although the hardness of Fe₂B would decline with increasing Mo content, Mo is an excellent candidate for improving the ductility of Fe₂B on the basis of the G/B and Poisson’s ratio ν values. The charge density plots indicate that the integral strength of the linear boron chains in [002] orientation is reduced in Mo-alloyed Fe₂B. The toughness improvement of Fe₂B would be attributed to the evolutions of B–B bonds, Fe/Mo–B bonds and Fe/Mo–Fe bonds, which may induce the deflection of the Fe₂B cleavage plane. Besides, the magnetic moments of these borides monotonically decrease with the increase in Mo content.

KEYWORDS:

• First-principles calculations
• Fe₂B
• mechanical properties
• electronic structure
• magnetic properties

Acknowledgements

The authors are especially grateful for scientific and technical support from High Performance Computing Center of CSU, China.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

^a Ref. [44].

^b Ref. [45].

^c Ref. [46].

Here, C₂₁ = C₁₂, C₃₁ = C₁₃, C₃₂ = C₂₃, C₄₅ = C₅₄, C₁₆ = C₆₁, C₆₂ = C₂₆ and C₃₆ = C₆₃.

^a Ref. [47].

^b Ref. [48].

^c Ref. [49].

^d Ref. [50].

^a Ref. [47].

^b Ref. [48].

^c Ref. [46].

^d Ref. [49].

^e Ref. [55]

Additional information

Funding

This work was supported by the double first-class discipline construction program of Hunan province, the Natural Science Foundation of Hunan Province (Grant No 2020JJ5274) and the Research Foundation of Education Bureau Hunan Province, China (Grant No 19B292).