Surface-directed and bulk spinodal decomposition compete to decide the morphology of bimetallic nanoparticles

An embedded-domain phase-field formalism is used for studying phase transformation pathways in bimetallic nanoparticles (BNPs). Competition of bulk and surface-directed spinodal decomposition processes their interplay with capillarity are identified as the main determinants BNP morphology. The former characterized by an effective driving force $\Delta\tilde{f}$ which increases decreasing temperature, while latter manifests itself through a balance interfacial energies captured contact angle $\theta$. simulated morphologies, namely, core-shell, Janus inverse cluster into distinct regions $\Delta\tilde{f}$-$\theta$ space. Variation $\theta$ Ag-Cu alloy system computed function temperature using CALPHAD approach surface estimated from modified Butler equation. This $\theta-\Delta\tilde{f}$ trajectory Ag-Cu, when superimposed on morphology map, enables prediction different morphological transitions temperature. Therefore, study establishes unique thermodynamic framework coupled simulations predicting tailoring nanoparticle variation processing