Understanding oxide surface stability: Theoretical insights from silver chromate

Silver chromate ($\mathrm{Ag_{2}CrO_{4}}$) has attracted considerable attention in recent years due to its promising photocatalytic performance, which strongly depends on the crystallographic orientation of its exposed surfaces. A detailed understanding of the structural stability of these surfaces under realistic conditions is therefore essential for advancing its applications. In this work, we combine density functional theory (DFT) with first-principles atomistic thermodynamics to systematically investigate the stability of multiple surface orientations and terminations of $\mathrm{Ag_{2}CrO_{4}}$. The surface Gibbs free energy was evaluated as a function of oxygen and silver chemical potentials, enabling the construction of stability trends under non-vacuum environments. Our results reveal that the degree of coordination of surface chromium-oxygen clusters plays a decisive role in determining surface stability. Furthermore, Wulff constructions predict morphology evolution as a function of external conditions, allowing us to identify the atomic structures of the exposed facets in the equilibrium crystal shape. These insights provide a fundamental framework for understanding surface-dependent photocatalytic activity in $\mathrm{Ag_{2}CrO_{4}}$ and related silver-based oxides.