On the strength of the halogen bonds: Mutual penetration, atomic quadrupole moment and Laplacian distribution of the charge density analyses

► The enhance of ΔχDX reflect in direct mode the strengthening of the XBs. ► Qzz(ΩX) increase in the sense Qzz(ΩF) < Qzz(ΩCl) < Qzz(ΩBr) < Qzz(ΩI). ► The depletion of ρ(r) on the X atom increases in the following order F < Cl < Br < I. ► ρ(r) is not increased in the direction of the bond forming (X⋯N). ► ∇2ρ(r) distribution on the VSCC on X atom shows where the transferred charge is.