A density functional study of CuO 2 molecules: structural stability, bonding and temperature effects (original) (raw)

Neutral and anionic CuO 2: an ab inito study

Computational Materials Science, 2000

By using first-principles calculations within density functional theory via the local density approximation (LDA) and the generalized-gradient approximation (GGA) of Perdew and Wang for exchange and correlation, we calculate the equilibrium structures of CuO2 and CuO2− clusters. In the case of CuO2, three isomers (OCuO linear and two CuO2 complexes, side-on and bent) lie within 0.5 eV, while the negatively charged cluster is most stable as a linear molecule. Our assignment of measured photo-electron spectra features on the basis of the electronic density of states (EDOS) suggests that the bent structure is the most stable among the two forms of CuO2− complexes.

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.

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.

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.

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.

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.

The ground state and electronic spectrum of CUO: a mystery

Faraday Discussions, 2003

Results are presented from a theoretical study of the lower electronic states of the CUO molecule. Multiconfigurational wave functions have been used with dynamic correlation added using second order perturbation theory. Extended basis sets have been used, which for uranium were contracted including scalar relativistic effects. Spin-orbit interaction has been included using the state-interaction approach. The results predict that the ground state of linear CUO is F 2 with the closed shell S þ 0 state 0.5 eV higher in energy. This is in agreement with matrix isolation spectroscopy, which predicts F 2 as the ground state when the matrix contains noble gas atoms heavier than Ne. In an Ne matrix, the experiments indicate, however, that CUO is in the S þ 0 state. The change of ground state due to the change of the matrix surrounding CUO cannot be explained by the results obtained in this work and remains a mystery.

Bulk and surface properties of Cu2O: A first-principles investigation

Journal of Molecular Structure: THEOCHEM, 2009

The bulk and surface properties of Cu 2 O were studied theoretically at the density-functional level (DFT). The calculated structural parameters, binding energy per Cu 2 O molecule (E u ) and electronic properties were compared with available experimental bulk data. The convergence of the surface energy was investigated for both non-polar (oxygen terminated) and polar (copper terminated) (1 1 1) surfaces. The electronic properties of both surfaces showed that there are surface states both at the top of the valence band and the bottom of the conduction band, indicating strong surface excitons decreasing the band gap. The structural relaxation was investigated for both cases. The study shows that the stoichiometric O-terminated Cu 2 O(1 1 1) surface exhibits minor relaxation, whereas the Cu-terminated surface undergoes extensive relaxation minimizing the surface polarity and indicative of surface reconstruction for this termination.

Electronic structure of the c(2×2)O/Cu(001) system

Physical Review B, 2002

The locally self-consistent real space multiple scattering technique has been applied to calculate the electronic structure and chemical binding for the c(2x2)O/Cu(001) system, as a function of d O−Cu1 -the height of oxygen above the fourfold hollow sites. It is found that the chemical binding between oxygen and copper has a mixed ionic-covalent character for all plausible values of d O−Cu1 . Furthermore, the electron charge transfer from Cu to O depends strongly on d O−Cu1 and is traced to the variation of the long-range electrostatic part of the potential. A competition between the hybridization of Cu1-d xz with O-p x , p y and Cu1-d x 2 −y 2 with O-p z states controls modification of the electronic structure when oxygen atoms approach the Cu(001) surface.