Projected density of states (PDOS) is a crucial concept in understanding electronic structures, particularly in relation to resonances and bond formation. PDOS provides insights into how different atomic orbitals contribute to the electronic states of a material, influencing its bonding characteristics. The relationship between PDOS and resonances is significant, as resonances can indicate the presence of unoccupied states that may facilitate bond formation. The choice of atomic toolkit, such as VASP or Quantum ESPRESSO, can affect the analysis of PDOS and its implications for material properties. Understanding these concepts is essential for predicting and manipulating chemical bonding in various materials.