For III-V compounds of light elements, while zb-BN is characterized by a large band gap (E g = 6.36(3) eV ), a value three times smaller is reported for zb-BP: E g ≈ 2.1 eV . In fact, boron nitride is polar covalent with significant charge transfer from B to N as opposed to BP where less charge transfer is expected. The difference in behavior has a chemical origin derived from the electronegativity () values according to Pauling: B= 2.04; N = 3.04 with (BN) = 1.