Understanding Atomic Site Disorder in Complex Materials*

Intermetallic alloys are a source of myriad emergent phenomena and promise advancements in material sciences.  However, experimental realization of predicted properties has proven challenging: Atomic disorder may be inevitable when thermodynamics at the temperature of material formation allow significant swapping of constituent elements. In this work, we present our initial steps toward predicting the properties of complex materials while taking into account the frequency and effects of atomic disorder. We will present first-order density-functional theory (DFT) calculations, within the plane-wave pseudopotential and projector-augmented-wave approaches, for a series of X₂YZ alloys in both full (L2₁) and inverse (XA) Heusler forms. To aid in understanding the frequency and property effects of X-Y site swapping, we choose Z-site elements shown experimentally to exhibit low site-swapping with X and Y sites. We will present spin polarizations, magnetic moments, density of states and band structures in the context of our obtained formation energies for each phase, making predictions of how properties of each system will change with atomic ordering in our future experimental efforts.