Quantum confinement and strong coulombic correlation in ZnO nanocrystals

Strong coulombic correlation interaction of quantum-confined system is studied by implementing a Hubbard-type mean-field potential in real-space pseudopotential method. Effective Hubbard U potential of a nanosized material is determined by atomic correlation potential and effective dielectric constant. We apply this method with spherically shaped wurtzite ZnO nanocrystals. Inefficient screening of Coulomb interaction in nanocrystalline system leads to a significant increase of effective U parameter compared to bulk solid. As a result, quasi-particle gap of nanocrystal increases noticeably with the U potential.