Moving to the B2 phases, the situation changes dramatically, particularly for K, Rb, and Cs. The p-states of these elements (Figures and), which constitute the semi-core shells, show a large dispersion in the density of states, creating a characteristic "U-like" shape. The enhanced dispersion in the DOSs can signify the formation of bonding and antibonding states in solid state. Ideally, the filled p-orbitals (np ) of the alkali metals should either form perfectly balanced bonding and anti-bonding states, i.e., a symmetric U-like shape in the DOSs, or a completely flat band if the p-orbitals are not interacting, resulting in a peaked DOS as in the B1 phase. Instead, the bonding region of the p-orbitals in projected-DOS (the one at lower energy) is more populated (higher DOSs) than the antibonding one. Does it mean that the semi-core p-orbitals of K, Rb, and Cs activate in the B2 phase, forming some intermetallic chemical bond at P ~ 1GPa? To discuss this possibility, we will now present the results from diverse chemical bonding analyses, specifically using the Crystal Orbital Hamilton Population (COHP), the Quantum Theory of Atoms in Molecules (QTAIM) and visualizing the crystalline orbitals. We will particularly focus on RbF as a general case for the heavy alkali metals.