Neutral and anionic CuO 2: an ab inito study (original) (raw)
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A density functional study of CuO 2 molecules: structural stability, bonding and temperature effects
Chemical Physics Letters, 2000
Structural and electronic properties of neutral and anionic CuO2 molecules are investigated within density functional theory. The lowest energy structures are the bent CuOO and the linear OCuO−. Consideration of temperature effects via first-principles molecular dynamics simulations allows to conclude that two CuO2− isomers (bent CuOO− and CuO2− side-on) coexist at very close energies in the measured photoelectron spectrum, for different spin states. Among the isomers of CuO2, bonding is the most covalent in the linear OCuO molecule.
Structural and electronic properties of small CuO m clusters
Applied Surface Science, 2004
The bonding between copper and oxygen atoms and its evolution with size has motivated extensive photoelectron spectroscopy measurements (see H. Wu, S. Desai, L.-S. Wang, J. Phys. Chem. A, 101 (1997) 2103–2777). Despite the small sizes involved in the experimental work carried out so far, the structure of the isomers is far from being elucidated. To go beyond qualitative interpretations, we have performed structural optimizations by using the first-principles molecular dynamics framework. The calculations on copper oxide clusters presented here are carried out within density functional theory (DFT), with a plane-wave basis set and generalized gradient corrections. Our results show that except in one case the CuO3 cluster takes a planar geometry, one of these isomers being an ozonide. The most stable isomer of CuO4 also exhibits planar geometry. Results obtained for CuO6 show that the symmetries deduced from the experiments do not correspond to the most stable forms, and are even unstable in some cases. More generally, the three largest clusters in the series are made of the structural blocks corresponding to the shape of the smaller isomers. Ozonides are favoured as the number of atoms increases.
Ground and Low-Lying States of Cu2+−H2O. A Difficult Case for Density Functional Methods
The Journal of Physical Chemistry A, 2004
The ground and low-lying states of Cu 2+-H 2 O have been studied using different density functional and post-Hartree-Fock methods. CCSD(T) results indicate that Cu 2+-H 2 O has C 2V symmetry and that the ground electronic state is a 2 A 1 state. At this level of theory the relative order of the electronic states is 2 A 1 < 2 B 1 < 2 B 2 < 2 A 2. However, density functional results show that the relative stabilities of these states vary depending on the degree of mixing of exact Hartree-Fock (HF) and density functional (DF) exchange. For pure generalized gradient approximation (GGA) functionals and also for hybrid functionals with percentages of HF mixing up to ∼20-25%, the 2 B 1 state becomes more stable than the 2 A 1 one. Moreover, with these functionals a C s (2 A′) structure is found to be the ground-state structure of Cu 2+-H 2 O. This is attributed to the fact that, for C 2V (2 B 1) and C s (2 A′), GGA functionals provide a delocalized picture of the electron hole, which is overstabilized due to a bad cancellation of the self-interaction part by the exchange-correlation functional. Among the different functionals tested, the one that provides better results compared to CCSD(T) is the BHLYP one.
STRUCTURAL AND ELECTRONIC PROPERTIES OF CuO, CuO2 AND Cu2O NANOCLUSTERS – A DFT APPROACH
Materials Science, 2015
The realistic structures of CuO, CuO 2 and Cu 2 O were completely optimized using density functional theory approach. The different structures were optimized to study the structural stability, dipole moment, point symmetry, HOMO-LUMO gap, ionization potential, electron affinity and binding energy of CuO, CuO 2 and Cu 2 O. The electronic properties of clusters were discussed in terms of HOMO-LUMO gap, density of states, ionization potential and electron affinity. This information will provide an insight for the synthesis of nanomaterials with proper geometry which finds its potential importance in engineering applications.
Identifying structural building blocks in CuO 6 clusters: CuO 2 complexes vs CuO 3 ozonides
Chemical Physics Letters, 2002
Structural minima of neutral and negatively charged CuO6 clusters have been investigated within density functional theory and a plane-wave approach. Among the lower energy structures, three isomers made of CuO2 complexes and two isomers featuring a double ozonide Cu(O3) unit lie within a few hundredths of eV. Isomers containing CuOOO chains are higher in energy. Formation of Cu(O3) units is accompanied by hybridization between O2p- and Cu3d-like states. We highlight analogies and differences between our results and the structural identification proposed in the framework of photoelectron spectroscopy experiments.
Physical review. B, Condensed matter, 1991
A neutral Cu(II) oxide CuO cluster with external point charges is studied in some detail. This cluster is small enough to allow the investigation of many-body effects by ab initio approaches. The electronic structure of the ground and low excited states as well as of core and valence ionic states of the cluster is discussed. We have thereby applied self-consistent-field, configuration-interaction, and Green's-function methods. The possibility is discussed that the cluster may serve as a model for solid-state Cu(II) oxides. The calculations show that the one-electron states of the cluster are strongly localized on either the copper or oxygen site. Strong screening effects are found to accompany the ioni. zation of both valence and core metal levels of the cluster and result in many-electron shakedown satellites in the spectra. These effects are connected with an intense charge-transfer process from the occupied 0 2p states to the vacant Cu 3do states in accord with predictions of nonparameter-free approaches (based on the Anderson impurity model, the Hubbard model, and other models) for the respective solid-state Cu(II) oxides. Connection is made with experimental x-rayphotoelectron and optical spectra. To substantiate the findings, the results of Green's-function calculations on ZnO and CuO clusters are also discussed, which are of interest by themselves.
Ab initio and density functional study of spectroscopic properties of CuO and CuS
Journal of Molecular Structure: THEOCHEM, 2006
Spectroscopic constants and molecular properties of CuO and CuS in their ground state have been studied in detail using B3LYP, MP2 and CCSD(T) methods. The basis set has been designed by testing the convergence and consistency of the calculated spectroscopic properties of these molecules and the final basis set is used for this calculation. The basis set of Cu (7s6p4d2f) has been built upon the basis set (6s3p3d) of Ahlrichs et al. and the basis sets for oxygen and sulfur are correlation consistent basis set. The spectroscopic properties of CuO and CuS obtained with CCSD(T) method in conjunction with these basis sets agree well with the experimental values wherever available for comparison. Most of the spectroscopic properties of CuO and CuS are new. The spectroscopic properties of CuS are first reported theoretically.
Quantum chemical assessment of the binding energy of CuO+
Journal of Chemical …, 2011
We present a detailed theoretical investigation on the dissociation energy of CuO + , carried out by means of coupled cluster theory, the multireference averaged coupled pair functional (MR-ACPF) approach, diffusion quantum Monte Carlo (DMC), and density functional theory (DFT). At the respective extrapolated basis set limits, most post-Hartree-Fock approaches agree within a narrow error margin on a D e value of 26.0 kcal mol −1 [coupled-cluster singles and doubles level augmented by perturbative triples corrections, CCSD(T)], 25.8 kcal mol −1 (CCSDTQ via the high accuracy extrapolated ab initio thermochemistry protocol), and 25.6 kcal mol −1 (DMC), which is encouraging in view of the disaccording data published thus far. The configuration-interaction based MR-ACPF expansion, which includes single and double excitations only, gives a slightly lower value of 24.1 kcal mol −1 , indicating that large basis sets and triple excitation patterns are necessary ingredients for a quantitative assessment. Our best estimate for D 0 at the CCSD(T) level is 25.3 kcal mol −1 , which is somewhat lower than the latest experimental value (D 0 = 31.1 ± 2.8 kcal mol −1 ; reported by the Armentrout group) [Int. J. Mass Spectrom. 182/183, 99 (1999)]. These highly correlated methods are, however, computationally very demanding, and the results are therefore supplemented with those of more affordable DFT calculations. If used in combination with moderately-sized basis sets, the M05 and M06 hybrid functionals turn out to be promising candidates for studies on much larger systems containing a [CuO] + core.