Variable-composition structural optimization and experimental verification of MnB₃and MnB₄

Abstract

In combination with variable-composition evolutionary algorithm calculations and first-principles calculations, we have systematically searched for all the stable compounds and their crystal structures in the extensively investigated binary Mn-B system. Our results have uncovered four viable ground-state compounds, with Mn2B, MnB, and MnB4, and previously never reported MnB3 and two metastable compounds, MnB2 and Mn3B4. Our calculations demonstrate that the early characterized mC10 structure of MnB4 showed dynamic instability with large imaginary phonon frequencies and, instead, a new mP20 structure is predicted to be stable both dynamically and thermodynamically, with a considerable energy gain and no imaginary phonon frequencies. The new MnB3 compound crystallizes in the monoclinic mC16 structure which lies 3.2 meV per atom below the MnB (oP8) ↔ MnB4 (mP20) tie-line at T = 0 K. Furthermore, these proposed phases have been verified by our annealed samples after arc-melting synthesis and corresponding powder XRD measurements.

Prediction of new high pressure phase of TaB3: First-principles

“…Transition metal borides with different boron contents have been studied experimentally and/or theoretically, such as ReB 2 [1][2][3][4], ReB 4 [5], WB 2 [6][7][8], WB 4 (WB 3 ) [9,10], MnB 3 [11], MnB 4 [11][12][13], TaB 2 [14][15][16][17] etc.. These compounds have excellent mechanical, as well as thermal and chemical properties.…”

Manganese mono-boride, an inexpensive room temperature ferromagnetic hard material

“…Among the six manganese borides, Mn 2 B is non-magnetic, MnB 2 and Mn 3 B 4 exhibits anti-ferromagnetic behavior and MnB 4 possesses paramagnetic property24252627. The absence of ferromagnetic spin order of other manganese borides is attributed to the insufficient interaction between the manganese atoms to stabilize the ferromagnetic spin order.…”

“…Manganese borides were one of the most promising transition metal (TM) borides because of their high hardness, low compressibility, high melting point, high electric conducting, wear resistance, thermal conduction and even room temperature magnetic properties24252627. Furthermore, from a more technological point of view, it is noteworthy that their INVAR behavior and high glass forming ability (GFA) to form bulk glass materials (BGMs) may be more useful in industrial applications62829.…”

Effect of Mn content in Fe(1−x)MnxB (x = 0, 0.25, 0.5, 0.75 and 1) on physical properties - ab initio calculations

“…The results in Table 3 indicate that Fe 1−x Mn x B have relatively strong anisotropic elastic constants resulting in the directional dependence of the moduli. Notably, the values of C 11 (C 66 ) are relatively smaller than those of C 33 (C 44 ) at 0 GPa, implying [25], exp2 [26] and exp3 [15], a [40], b [41] that the intra-layer chemical bonds are weaker than those between the layers.…”