Kernel-differentiated fusion strategy redefines critical size thresholds in giant twinned-FCC RS-AuNCs: unlocking size adaptability and birth of metallicity

Abstract

Thiolate-protected gold nanoclusters (RS-AuNCs) have emerged as an ideal research system for unveiling intrinsic structure–property correlations due to their atomically precise structural tunability. This study addresses the structural absence and configuration stability controversies of face-centered cubic (FCC)-configured RS-AuNCs in the large-size regime of 102–191 gold atoms by establishing an innovative theoretical analysis framework. Through density functional theory (DFT) calculations, we successfully predicted for the first time a twinned-FCC Au₁₂₇(SR)₄₈ structure with C₂ symmetry (Au₁₂₇-x), which exhibits a remarkably small energy difference of merely 0.03 eV compared to the lowest-energy D_h configuration (Au₁₂₇-w). This discovery strongly confirms the thermodynamic feasibility of FCC configurations in the 102–144 atom range. By integrating the ‘kernel-differentiated fusion’ growth mechanism with the ‘divide-and-protected’ assembly strategy, we systematically constructed three large-sized FCC cluster models: Au₁₆₄(SR)₆₀, Au₁₈₂(SR)₆₆ and Au₁₈₈(SR)₆₆. The calculated average formation energies (E_ave) validate the exceptional structural stability of these clusters. Strikingly divergent evolution patterns in HOMO–LUMO gaps are observed between shell-structured and cubic FCC-type RS-AuNCs across varying sizes, unambiguously demonstrating configuration-governed electronic structure modulation. More crucially, UV-Vis absorption spectra unveil emergent metallic signatures in both Au₁₈₂(SR)₆₆ and Au₁₈₈(SR)₆₆ clusters, thereby fundamentally redefining the critical size threshold for incipient metallicity in FCC-type RS-AuNCs. Breaking through traditional theoretical frameworks centered on ‘size-configuration preference’, this research first elucidates the potential stability of FCC-configured RS-AuNCs within controversial size ranges. It not only addresses the existing size gap in structural models of large RS-AuNCs but also establishes a novel configuration design paradigm based on a ‘kernel-differentiated fusion’ strategy.