| Abstract Scope |
Solute segregation (adsorption) at grain boundaries (GBs), which is ubiquitous in polycrystalline materials and can remarkably alter various properties, is one of the classic materials science problems. However, the understanding of the atomic level GB segregation structures is still limited, mostly to symmetric GBs. Here, we combine the aberration-corrected electron microscopy and first-principles density functional theory (DFT) calculations to reveal a highly asymmetric interfacial superstructure in WC. First, DFT calculated segregation energies verify the asymmetric segregation structures of Ti and Co in an WC GB as observed in experiment. Second, the analysis of charge density difference, coordination number, and bonding environments explain that why a W-rich layer with less segregation can separate Ti-rich and Co-rich segregation layers, both occurring off the GB center. Finally, we introduce a new descriptor, sum of bond ordering (SBO), which can be used to predict segregation trends in complicated interfacial structures. |