<P> After the development of quantum mechanics, two basic theories were proposed to provide a quantum description of chemical bonding: valence bond (VB) theory and molecular orbital (MO) theory . A more recent quantum description is given in terms of atomic contributions to the electronic density of states . </P> <P> In COOP, COHP and BCOOP, evaluation of bond covalency is dependent on the basis set . To overcome this issue, an alternative formulation of the bond covalency can be provided in this way . </P> <P> The center mass cm (n, l, m, m) of an atomic orbital n, l, m, m ⟩, with quantum numbers n, l, m, m, for atom A is defined as </P> <Dl> <Dd> c m A (n, l, m l, m s) = ∫ E 0 E 1 E g n, l, m l, m s ⟩ A (E) d E ∫ E 0 E 1 g n, l, m l, m s ⟩ A (E) d E (\ displaystyle cm ^ (\ mathrm (A)) (n, l, m_ (l), m_ (s)) = (\ frac (\ int \ limits _ (E_ (0)) \ limits ^ (E_ (1)) Eg_ (n, l, m_ (l), m_ (s) \ rangle) ^ (\ mathrm (A)) \ left (E \ right) dE) (\ int \ limits _ (E_ (0)) \ limits ^ (E_ (1)) g_ (n, l, m_ (l), m_ (s) \ rangle) ^ (\ mathrm (A)) \ left (E \ right) dE))) </Dd> </Dl>

What is an example of an covalent bond