Simulated dependence of peak reflectivity $R_{\max }$ and integrated reflectivity $R_{\mathrm{int}}$ on density contrast $\mathrm{\Delta }\rho$ for a [W/SiC]₄₀ ML with period d = 3 nm, stacking ratio Γ = 0.5, and interfacial roughness σ = 0.1 nm. The tungsten density is varied from bulk value (19.25 g cm⁻³) down to that of SiC (3.16 g cm⁻³). Inset: first Bragg peak profiles versus grazing angle θ for selected Δρ values.