Study of structural, electronic, optical and thermal properties of refractory material (CrAlB)

An ab initio investigation of the temperature-dependent energetic barriers towards CrAlB and (Mo,Cr)AlB formation in a metastable synthesis scenario

“…2b) is considered, it is immediately evident that several Cr-rich (Mo,Cr)AlB phases are unstable (ΔE f > 0), both for the ternary composition CrAlB (x = 1) and for quaternary compositions with low Mo content, such as Mo 0.125 Cr 0.875 AlB. This corresponds to prior findings for CrAlB [17][18][19][20] and may partially explain the lack of successful experiments synthesizing that phase in equilibrium, as alluded to in the introduction. Conversely, it is also evident that addition of Mo does indeed stabilize the quaternary system, with x ≈ 0.8 (corresponding to a Mo/Cr ratio of 1/5) sufficient for phase formation if MoB and Cr 2 AlB 2 are the competing phases.…”

“…This is in stark contrast to other phases in the ternary Cr-Al-B system of non-equistoichiometric composition such as Cr 2 AlB 2 , Cr 3 AlB 4 and Cr 4 AlB 6 7,15 as well as Cr 4 AlB 4 , 16 all of which have been obtained experimentally. This discrepancy has been partially explained by theoretical studies such as those by Bai et al 17 and Khazaei et al, 18 which have shown the hypothetical CrAlB phase to be unstable vs. the competing phase Cr 2 AlB 2 and Al in the ground state at 0 K, while being stable upon formation from the elements, with the latter finding also reported by Rastogi et al 19 and Wei et al 20 It was also observed, via electronic structure analysis and force constant calculations, that the B-B bonds are strongest in CrAlB, followed by the Cr-B bonds, with Cr-Al and Al-B bonds being significantly weaker, 17,18 allowing for extrapolations of the mechanical properties. 17 However, while reporting both enthalpies of formation (ΔH) and Gibbs reaction energies (ΔG) in the ground state, none of the hitherto published theoretical studies, to our knowledge, examined the temperature dependence ΔG(T ) of the Gibbs energy, either vs. the elements or competing phases.…”

Ab‐initio study of electronic, optical, thermal, and transport properties of Cr4AlB6

“…They also reported that these compounds are brittle as well as have metallic bond. Very recently, various properties of CrAlB, Cr 2 AlB 2 , and Cr 3 AlB 4 have also been studied …”