Valence-band electronic structure of TiZrNbCuCo high-entropy alloy: Ab initio calculations and X-ray photoemission

We report core results of combined theoretical and experimental study of the valence band struc-ture of TiZrNbCuCo equiatomic high entropy alloy as a potentially novel catalyst by combiningDensity Functional Theory ab initio (ai) calculations with X-ray photoemission spectroscopy. Cal-culations based on a 16-atom model on a body centered cubic (BCC) lattice are compared withspectra measured for the amorphous alloy using 350 eV photons. The calculated element-resolveddensities of states (PDOS), weighted by the corresponding photoionization cross-sections, reproducethe main features of the experimental spectrum with good semi-quantitative agreement. Deconvo-lution of the measured spectrum further supports the calculated peak positions associated with Cu,Co, and Nb, with particularly close agreement for the Cu and Co contributions. Site-resolved calcu-lations reveal a strong dependence of the Co and early transition metals (Ti,Zr,Nb) electronic stateson the local atomic environment, whereas the Cu states are comparatively insensitive to changesin neighboring atoms. Ti, Zr, and Nb contribute approximately 76% of the calculated density ofstates at the Fermi level, unlike the Co contribution of approximately 21%, which is consistentwith the absence of band crossing at the equiatomic composition and with previously reported alloyproperties. These results show that a computationally modest structural model can capture theprincipal valence-band features of this HEA and provide useful insight into the electronic structureof compositionally complex transition-metal alloys.