The Royal Society of Chemistry has been contacted by a reader who informed us there were errors in the computational method-ology applied in this work;the main concern is related to the fact that the geometry and band...The Royal Society of Chemistry has been contacted by a reader who informed us there were errors in the computational method-ology applied in this work;the main concern is related to the fact that the geometry and band gap are reported to be unchanged with an increase in the number of layers in the 100 surface.As part of our investigation,we consulted with independent experts who also raised concerns over the methodology,describing it as fundamentally flawed on the basis that the slab models are identical to a supercell of the primitive cell,and therefore do not give information about the surfaces,concluding that the slabs in this paper have no physical meaning.展开更多
Density functional theory(DFT)calculations have been performed on 1 to 9 layers of Cu_(2)O(100),(111),and(110)planes to further understand the electronic band structures and the origin of the facet-dependent propertie...Density functional theory(DFT)calculations have been performed on 1 to 9 layers of Cu_(2)O(100),(111),and(110)planes to further understand the electronic band structures and the origin of the facet-dependent properties of Cu_(2)O crystals.The(100)planes show an invariant band structure with a constant band gap of 1.787 eV like that of a primitive cell.The(111)planes present a periodicity of every three layers with band gaps varying between zero and 1.787 eV.An unusual periodicity of every two layers has been found for the(110)planes oscillating between 1.787 eV and very small band gaps including a zero band gap.By comparing the valence band edges of different plane layers and the position of the Fermi level in the density of states(DOS)diagrams,relative valence band bending of the Cu_(2)O{100},{111},and{110}surfaces can be drawn to explain their strongly facet-dependent electrical conductivity properties.Moreover,while the(100)planes show a fixed crystal lattice with a tunable number of planes,the calculations identify slight bond length deviations and bond distortion for the(111)and(110)planes.The partial density of states(PDOS)diagrams also reveal(111)and(110)plane layer-dependent variations in the frontier orbital electron energy distribution.The structural perturbations at crystal surfaces can yield different barrier heights to charge transport across the{100},{111},and{110}faces,and photons of different wavelengths should get absorbed in the thin surface layer to produce the observed optical facet effects.Such lattice perturbations should be present in other semiconductor materials as surface-dependent behaviors are broadly observable in many semiconductors.展开更多
Semiempirical quantum chemical method AM1 was employed to calculate the highest occupied molecular orbital (HOMO) energy levels (E-HOMO) for various types of antioxidants. It was verified that the correlation between ...Semiempirical quantum chemical method AM1 was employed to calculate the highest occupied molecular orbital (HOMO) energy levels (E-HOMO) for various types of antioxidants. It was verified that the correlation between logarithm of free radical scavenging rate constants (1gks) and E-HOMO substantially arises from the correlation between E-HOMO and O-H bond dissociation energies (BDE) of antioxidants. Furthermore, E-HOMO were poorly correlated with the logarithm of relative free radical scavenging rate constants (1gk(3)/k(1)) for various types of antioxidants that possess complex structures (r = 0.5602). So in a broad sense, E-HOMO was not an appropriate parameter to characterize the free radical scavenging activity of antioxidants.展开更多
文摘The Royal Society of Chemistry has been contacted by a reader who informed us there were errors in the computational method-ology applied in this work;the main concern is related to the fact that the geometry and band gap are reported to be unchanged with an increase in the number of layers in the 100 surface.As part of our investigation,we consulted with independent experts who also raised concerns over the methodology,describing it as fundamentally flawed on the basis that the slab models are identical to a supercell of the primitive cell,and therefore do not give information about the surfaces,concluding that the slabs in this paper have no physical meaning.
文摘Density functional theory(DFT)calculations have been performed on 1 to 9 layers of Cu_(2)O(100),(111),and(110)planes to further understand the electronic band structures and the origin of the facet-dependent properties of Cu_(2)O crystals.The(100)planes show an invariant band structure with a constant band gap of 1.787 eV like that of a primitive cell.The(111)planes present a periodicity of every three layers with band gaps varying between zero and 1.787 eV.An unusual periodicity of every two layers has been found for the(110)planes oscillating between 1.787 eV and very small band gaps including a zero band gap.By comparing the valence band edges of different plane layers and the position of the Fermi level in the density of states(DOS)diagrams,relative valence band bending of the Cu_(2)O{100},{111},and{110}surfaces can be drawn to explain their strongly facet-dependent electrical conductivity properties.Moreover,while the(100)planes show a fixed crystal lattice with a tunable number of planes,the calculations identify slight bond length deviations and bond distortion for the(111)and(110)planes.The partial density of states(PDOS)diagrams also reveal(111)and(110)plane layer-dependent variations in the frontier orbital electron energy distribution.The structural perturbations at crystal surfaces can yield different barrier heights to charge transport across the{100},{111},and{110}faces,and photons of different wavelengths should get absorbed in the thin surface layer to produce the observed optical facet effects.Such lattice perturbations should be present in other semiconductor materials as surface-dependent behaviors are broadly observable in many semiconductors.
文摘Semiempirical quantum chemical method AM1 was employed to calculate the highest occupied molecular orbital (HOMO) energy levels (E-HOMO) for various types of antioxidants. It was verified that the correlation between logarithm of free radical scavenging rate constants (1gks) and E-HOMO substantially arises from the correlation between E-HOMO and O-H bond dissociation energies (BDE) of antioxidants. Furthermore, E-HOMO were poorly correlated with the logarithm of relative free radical scavenging rate constants (1gk(3)/k(1)) for various types of antioxidants that possess complex structures (r = 0.5602). So in a broad sense, E-HOMO was not an appropriate parameter to characterize the free radical scavenging activity of antioxidants.
