As miniaturization of electronic devices is rapidly approaching the nanoscale, a deeper understanding of the electronic and structural properties of silicon nanoclusters, called to be the next-generation materials for circuit design, becomes of paramount importance. Herein, a detailed density functional theory study of the binding forces between [20]silafullerenes frameworks and their central halide ions is conducted, prompted by the recent synthesis of the first discrete Si20 dodecahedra stabilized by an endohedral chloride and valence saturation, [Cl@Si32Cl44]-, as well as the fabrication of the first electron transistor device based on a single silicon cluster. Although more intense stabilizing forces are obtained in the chloride-containing system, a small energetic difference with respect to bromide-centered one is found (4.76 kcal mol-1) suggesting the synthetic accessibility of the latter. An energy decomposition analysis is conducted revealing that in all cases (representing about 71%) the electrostatic term is the major contributor to the binding forces. Additionally, the higher-order electrostatic terms become more relevant as the halide volume increases and this effect is quantified through a local multipole analysis. This methodology enables us to state that those silicon atoms directly linked to peripheral chlorines play a more relevant role into the guest encapsulation than those attached to trichlorosilyl. It is also evidenced that the presence of the peripheral groups deeply influences the charge of the inner cluster cavity making it more positive and suitable for the encapsulation of the halide anions. We expect that this research will allow a better understanding of the driven forces of these novel structures, also contributing to experimental teams searching for novel building blocks for nanoscale transistors.