A key drawback of the IGM method is that its isosurfaces are usually quite bulgy, which not only hinders visual analysis but may also cause unreasonable coloring of the isosurfaces. This occurs because the isosurfaces are often over-extended to areas very close to the nuclei, where electron density is much higher than in the interatomic interaction regions. To address this issue, we proposed a variant of the IGM method called IGM based on the Hirshfeld partition of molecular electron density (IGMH), which has been widely employed in the literature in recent years. In this method, the density of free-state atoms in Eqs. ( ) and ( ) is replaced by the atomic electron density 𝜌 𝑖 IGMH (𝐫) = 𝜌(𝐫)𝑤 𝑖 (𝐫), where ρ is the actual electron density of the system, and 𝑤 𝑖 (𝐫) = 𝜌 𝑖 free /𝜌 pro is the Hirshfeld atomic weighting function. Additionally, the derivative of 𝜌 𝑖 IGMH with respect to the Cartesian components, which is needed in the IGMH analysis, is evaluated in a specific way. It should be noted that there is another approach to realizing IGM analysis based on the actual electron density, which involves the gradient-based partition (GBP) scheme, referred to as IGM(GBP). However, the principle of IGM(GBP) is more complicated and has not become as popular as IGMH.