Ab initio calculation of the bcc Fe–Al phase diagram including magnetic interactions

Electron theoretical investigation of the stability of the B2-TiFe compound

“…Quantitatively, however, experimental and calculated diagram disagree, in the sense that the temperature scale of the later is considerably higher than that of the former. This has been observed also in a previous ab initio calculation in system BCC Fe-Al by the present authors [20] and was attributed to a missing degree-of-freedom in the thermodynamic description of the system. One possible origin for this discrepancy in the temperature scale would be the use of the rigid lattice approximation.…”

“…This was tested by performing a separate calculation using the spin s = 1 Ising model for iron, with the parameters and procedure described in Ref. [20]. This resulted in negligible changes in the phase diagram topology when the phase diagram was plotted in the scale of Fig.…”

“…These parameters are calculated from the ab initio formation energies by the procedure detailed in Ref. [20].…”

Combined ab initio and experimental study of A2 + L21 coherent equilibria in the Fe–Al–X (X = Ti, Nb, V) systems

“…For example, the maximum experimental critical temperature for the B2/A2 equilibria is estimated to be around 1750 K, while the present calculation leads to a maximum temperature at 3225 K. Instead of this, the calculated critical temperature for the DO 3 /B2 equilibria is found at 553 K while it is experimentally found till 823 K. This kind of inconsistency where the ab initio calculations overestimates and underestimates the experimental critical temperatures of two different continuous transformations in the same alloy system has been previously reported. Gonzales-Ormeño et al [51], working also in the binary FeeAl phase diagram, had obtained a value of 625K for the DO 3 /B2 second order transformation and a similar value that the one found in this work for the B2/A2 transformation. We have attempted to include the vibrational entropies of formation through the Debye-Grüneisen model [52], this contribution could partially account for that fact, raising the critical temperature for the DO 3 /B2 equilibria to 683 K and lowering the maximum B2/A2 equilibria temperature to 2873 K. This correction was not extended to the ternary calculations since it was not enough to account for the discrepancies with experimental values.…”

Initial Oxidation of Fe–Al and Fe–Cr–Al Alloys: Cr as an Alumina Booster

“…It was found that 506 (for bulk) and 231 (for surfaces) uniformly distributed k-vectors in the irreducible part of the 3D and 2D Brillouin zones were enough for present purposes. The alloys were described as substitutionally disordered ferromagnetic bcc alloys [36,37].…”