Short-Range-Order for fcc-based binary alloys Revisited from Microscopic Geometry

摘要

Short-range order (SRO) in disordered alloys is typically interpreted ascompetition between chemical effect of negative (or positive) energy gain bymixing constituent elements and geometric effects comes from difference ineffective atomic radius. Although we have a number of theoretical approaches toquantitatively estimate SRO at given temperatures, it is still unclear tosystematically understand trends in SRO for binary alloys in terms of geometriccharacter, e.g., effective atomic radius for constituents. Since chemicaleffect plays significant role on SRO, it has been believed that purelygeometric character cannot quantitatively explain the SRO trends. Despite theseconsiderations, based on the density functional theory (DFT) calculations onfcc-based 28 equiatomic binary alloys, we find that while convensionalGoldschmidt or DFT-based atomic radius for constituents have no significantcorrelation with SRO, atomic radius for specially selected structure,constructed purely from information about underlying lattice, can successfullycapture the magnitude of SRO. These facts strongly indicate that purelygeometric information of the system plays central role to determinecharacteristic disordered structure.