 Multipole density formalism

Multipole density formalism is a theoretical framework used to describe the electronic distribution within molecules and materials by expanding the electron density in terms of multipole moments. This approach is particularly useful in quantum chemistry and condensed matter physics to analyze and visualize electronic structures. ### Key Features of Multipole Density Formalism: 1. **Electron Density Expansion**: The electron density \(\rho(\mathbf{r})\) of a system can be expanded in terms of a series of multipole moments.