First-principles investigation of Cr-doped Fe2B: Structural, mechanical, electronic and magnetic properties

Abstract The structural, mechanical, electronic and magnetic properties of Fe 8−x Cr x B 4 (x = 0, 0.25, 0.5, 1, 2, 3, 4, 5, 6, 7 and 8) have been investigated by first-principles calculation. It was found that the calculated structural parameters are well consistent with available experimental data. Moreover, all studied compounds are thermodynamically stable phases. On the whole, the moduli of the compounds firstly increase and then decrease with the increase of Cr concentration, whereas the variation of hardness exhibits more fluctuations. All Cr-doped Fe 2 B have better ductility than Fe 2 B except Fe 2 Cr 6 B 4 and Fe 5 Cr 3 B 4 . Interestingly, Fe 4 Cr 4 B 4 is of not only the slightly larger hardness, but also much better ductility than Fe 2 B. As the Cr concentration is lower than 20 wt%, the hardness of Cr-doped Fe 2 B slightly decreases with increasing Cr, whereas the sharply increased hardness of (Fe, Cr) 2 B in Fe-B alloys or boriding layer should be attributed to the multiple alloying effects resulting from Cr and the other alloying elements. The electronic structures revealed that the Fe-B and/or Cr-B bonds are mainly responsible for their mechanical properties, and the M-N (M = Fe or Cr, N = Fe or Cr) bonds in 〈2 2 0〉 and 〈1 1 3〉 orientations show covalent character. Additionally, the magnetic moments (Ms) of the compounds do not monotonically decrease with increasing Cr.