New Proximate Structures for {110}(111)-Type Antiphase Boundaries in BCC-Derived Ordered Intermetallics

A new model, known as the diffuse multi-layer fault model (DMLF), has provided an accurate high-throughput method for evaluating the energetics of planar faults within alloys of complex composition. Specifically, the DMLF, which approximates a planar fault through a series of proximate structures that capture the local bonding environment within the vicinity of the fault, has been used recently to assess the energetics of planar faults within FCC alloys [1] as well as the {111}a/2(110) antiphase boundary observed within FCC-derived L1₂ ordered intermetallics. [2] Within this work, we report on the successful extension of this model to the antiphase boundaries present on {110} planes within the BCC-derived B2 and L2₁ordered intermetallics. Through coupling the DMLF to a large database of symmetrically distinct atomic configurations on a host BCC lattice, proximate structures have been identified for the {110}a/2(111) antiphase boundary within the B2 and L2₁ intermetallic and the {110}a/4(111) antiphase boundary observed in the L2₁ intermetallic. Density functional theory calculations are employed to validate the accuracy of the formation energies of these newly identified proximate structures relative to those calculated <i>via</i> the more conventional, and computationally costly, supercell method. The use of the B2 and L2₁ proximate structures to predict the thermodynamic stability of planar faults in BCC-derived ordered intermetallics with a complex composition will also be discussed.<br/><br/>[1] K. V. Vamsi, M. A. Charpagne, and T. M. Pollock, "High-throughput approach for estimation of intrinsic barriers in FCC structures for alloy design," <i>Scr. Mater.</i>, 204, 114126.<br/>[2] K. V. Vamsi and T. M. Pollock, "A new proximate structure for the APB (111) in L12 compounds," <i>Scr. Mater.</i>, 182, 38-42.