The formula for electron density difference (Δρ) in Equation (13) is cited as originating from reference [53], but upon reviewing the cited paper (Zheng et al., 2023, Appl. Surf. Sci.), I could not find this specific equation or its derivation. This raises concerns about the accuracy of the citation and the potential misattribution of prior research.
Could the authors clarify whether this formula was derived from another source or independently formulated?