The structural and electronic properties of ZnO (1010) and (1120) surfaces were investigated by means of density functional theory applied to periodic calculations at B3LYP level. The stability and relaxation effects for both surfaces were analyzed. The electronic and energy band properties were discussed on the basis of band structure as well as density of states. There is a significant relaxation in the (1010) as compared to the (1120) terminated surfaces. The calculated direct gap is 3.09, 2.85, and 3.09 eV for bulk, (1010), and (1120) surfaces, respectively. The band structures for both surfaces are very similar.
Understanding
the antioxidant activity of flavonoids is important
to investigate their biological activities as well as to design novel
molecules with low toxicity and high activity. Aromaticity is a chemical
property found in cyclic structures that plays an important role in
their stability and reactivity, and its investigation can help us
to understand the antioxidant activity of some heterocyclic compounds.
In the present study, we applied the density functional theory (DFT)
to investigate the properties of seven flavonoid structures with well-reported
antioxidant activity: flavan, anthocyanidin, flavanone, flavonol,
isoflavone, flavone, and flavan-3-ol. Conformational, structural,
magnetic, and electronic analyses were performed using nuclear magnetic
resonance, ionization potentials, electron affinity, bond dissociation
energy, proton affinity, frontier molecular orbitals (highest occupied
molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO)),
and aromaticity through nucleus-independent chemical shifts to analyze
these seven flavonoid structures. We revised the influence of hydroxyl
groups on the properties of flavonoids and also investigated the influence
of the aromaticity of these seven flavonoids on the antioxidant activity.
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