Impact of spatial confinement on the substitutional doping of Ca and P atoms in bulk, surface, and Cu cluster systems

Abstract Understanding the electronic structure of Cu and how it changes in bulk, surface and cluster after Ca and P doping is a key aspect in catalysis and material science. The present study comprises density functional theory (DFT) calculations of Ca and P incorporation and adsorption into Cu systems across three dimensionalities: bulk (3D), Cu (100) surface (2D), and Cu 19 clusters (0D).Systematic analysis of substitution and adsorption configurations revealed different mechanismsfor the incorporation of the two dopants. Ca exhibited weak interaction with Cu with minimal p-d orbital hybridization across all systems, requiring positive substitution energies of 2.91 eV in bulk to 0.81 eV on surface, and acting primarily as localized electronic perturbations. In contrast, P demonstrated strong energy interactions, characterized by extensive covalent bonding and negative substitution energies of -0.85 eV into the bulk system to -1.71 eV on the surface. Furthermore, significant modification of the Cu electronic structure through p-d orbital overlapping was observed, where dimensional confinement effects became increasingly important at smaller scales.At 0D dopant-cluster interactions were enhanced compared to bulk and surface systems. Similarly, at 0D and 2D, high coordination sites exhibiting the strongest electronic coupling. The electronic structure analysis through density of states calculations confirms that while Ca preserves the metallic character of Cu with minor perturbations, P fundamentally alters the electronic properties through the formation of covalent bonds.