An Atlas and Design Rules for Single- and Dual-Atom Alloys

Abstract

A long-standing goal across heterogeneous catalysis, materials science, and condensed matter physics is to design alloys with prescribed local atomic arrangements. Recent experiments show that dilute trimetallic alloys unlock chemistries inaccessible to bimetallics, but realizing this potential requires knowing which dopant structures form across an enormous compositional space. Using density functional theory screening, we construct an atlas spanning transition metal single- and dual-atom alloys in Cu and Ag surfaces, which we validate by scanning tunneling microscopy. The stability follows an electron count: dopants pair most strongly when their combined d-electron count approaches ten. Host metal and surface facet can be used to tune the resulting active site motifs, while size mismatch and spin explain variations around this trend. We further introduce a reactor-anchor concept, in which one dopant anchors a second, otherwise bulk-segregating dopant at the surface. Together, these results establish design principles for engineering alloys with targeted active site structures.