First-principles prediction and preparation of high-entropy carbonitride ceramics

First-principles calculation predictions combined with experimental preparation were performed on equimolar five-component high-entropy carbonitrides(HECN). A supercell (SC) model suitable for disordered dual-sublattice systems was constructed, and the computational parameters were systematically optimized. The formation energies, mixing enthalpies and mixing entropies of 126 candidate systems consisting of group IVB, VB and VIB transition metals were calculated systematically. Among these candidates, HECN-1 (TiZrHfNbTa)(C 0.6 N 0.4 ) possesses the most negative formation energy of −1.143 eV/atom, while HECN-126 (VTaCrMoW)(C 0.6 N 0.4 ) has the least negative formation energy of −0.348 eV/atom. The modulation mechanism of transition metal species on the energetic favorability relative to pure elemental reference phases was systematically revealed, and the microscopic origin stemming from the synergistic effects of valence electron concentration (VEC) and delocalized d-orbitals was clarified from the perspective of electronic structure. We classify the nine constituent elements into three groups according to their contributions to the elemental-reference energetic favorability of HECNs: favorable group (Hf, Ta, Ti), moderate group (Zr, Nb, Mo), and unfavorable group (W, V, Cr). On this basis, target compositions with superior energetic favorability relative to pure elemental reference phases were screened, and HECN-1, HECN-5 and HECN-11 powders were successfully synthesized via atmosphere sintering. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) characterizations verify the formation of single-phase solid solutions. The DFT calculations show that all 126 candidate compositions have negative formation energies relative to pure elemental reference phases, which indicates that these high-entropy carbonitrides possess energetic advantages for formation. Furthermore, the incorporation of Group IVB and VB transition metals can effectively reduce the formation energy of the system. Such regularity is governed jointly by VEC-regulated bonding/antibonding orbital occupation and covalent-bond strength tuned by d-orbital delocalization. This study provides a reliable route for compositional design and experimental fabrication of high-entropy carbonitrides.