We study the local electronic structure of an equimolar-multimetal solid solution of high-entropy metal disulfide $\left(\mathrm{Fe},\mathrm{Co},\mathrm{Ni},\mathrm{Cu}\right){\mathrm{S}}_2$ and its parent compounds ${M\mathrm{S}}_2$ $(M=\mathrm{Fe}, \mathrm{Co}, \mathrm{Ni}, \text{and} \mathrm{Cu})$ using x-ray absorption spectroscopy (XAS). The Fe, Co, and Ni $L_{2,3}$-edge absorption spectra indicate a divalent metal state both in ${(\mathrm{Fe}, \mathrm{Co}, \mathrm{Ni}, \mathrm{Cu})\mathrm{S}}_2$ and its parent compounds, except for the Cu $L_{2,3}$-edge absorption spectra. The Cu $L_{2,3}$-edge spectra of ${\mathrm{CuS}}_2$ and $\left(\mathrm{Fe},\mathrm{Co},\mathrm{Ni},\mathrm{Cu}\right){\mathrm{S}}_2$ show satellites, which rule out the divalent Cu but can be analyzed as a combination of monovalent and trivalent copper states. The $L_{2,3}$-edge XAS spectral analysis with charge-transfer multiplet cluster model calculations was carried out for $\left(\mathrm{Fe},\mathrm{Co},\mathrm{Ni},\mathrm{Cu}\right){\mathrm{S}}_2$ and its parent compounds. The estimated electronic parameters indicate a negative charge-transfer energy for the parent compounds and high-entropy compound (with the Ni L edge in the high-entropy compound being an exception), which corresponds to a p-p type lowest energy excitation in the extended Zaanen-Sawatzky-Allen phase diagram. The analysis shows that the charge-transfer energy $\mathrm{\Delta }$ decreases and the on-site Coulomb energy $U_{dd}$ increases systematically from Fe to Cu. The results suggest that in the high-entropy compound compared to the parent compounds, the hybridization strengths are weaker for Fe $3d\text{−}\mathrm{S}$ $3p$ and Co $3d\text{−}\mathrm{S}$ $3p$ and stronger for Ni $3d\text{−}\mathrm{S}$ $3p$ and Cu $3d\text{−}\mathrm{S}$ $3p$ bonds. This behavior is consistent with the longer Fe-S and Co-S bond distances and shorter Ni-S and Cu-S bond distances in the high-entropy compound compared to the parent compounds. The results indicate modifications in the structural lattice parameters of the high-entropy compound are reflected in the electronic structure and provides evidence for the so-called cocktail effect in the high-entropy compound.

• Received 31 January 2024
• Revised 16 April 2024
• Accepted 17 April 2024

DOI:https://doi.org/10.1103/PhysRevB.109.195129