STRUCTURAL AND ELECTRONIC PROPERTIES OF CuO, CuO2 AND Cu2O NANOCLUSTERS – A DFT APPROACH (original) (raw)
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Journal of Nepali Physical Society, 2020
The structural, electronic and magnetic properties of the nanoclusters of (Cu 2 O) n= 1, 2, 3 and (CuO) m = 2, 4, 6 have computationally studied. Density Functional Theory incorporated in Atomistic tool kit (ATK-DFT) calculators with exchange-correlation functional (SGGA+U) based ab-initio approach is applied for simulation and calculation of these nanoclusters. In the computational study, the nanoclusters (Cu 2 O) 1 , (Cu 2 O) 3 , (CuO) 2 and (CuO) 6 show semiconducting behavior whereas (Cu 2 O) 2 and (CuO) 4 show semimetallic behaviors. The nanoclusters (Cu 2 O) 1 and (Cu 2 O) 3 show diamagnetic, (Cu 2 O) 2 and (CuO) 4 show ferromagnetic, (CuO) 2 and (CuO) 6 show antiferromagnetic behaviors. The magnetic moments 0.28µ B and 0.03 µ B are observed in the nanoclusters (Cu 2 O) 2 and (CuO) 4 while others are found to be as nonmagnetic. The total energy of nanoclusters have found to be decreasing towards total minimum energy with increasing number of atoms of copper oxides. The nanoclusters (Cu 2 O) n = 1, 2, 3 and (CuO) m = 2, 4, 6 are used in various applications as in the synthesis of technological materials. The analysis of the effects of bond length and binding energy with the size of nanoclsters have been presented.
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.
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.
Density Functional Theory Study of Copper Clusters
The Journal of Physical Chemistry B, 1999
A density functional theory study of copper clusters is presented. Fully optimized geometries, electronic structures, HOMO-LUMO gaps, spin density distributions, and ionization potentials are reported. The study is systematic starting with one-dimensional clusters followed by several planar structures and three-dimensional systems chosen to emulate (100) and (111) planes of bulk Cu. For the 1-D systems, it is found that the dissociation energy and ionization potential follow an oscillatory behavior that reflects a conjugate-like character indicative of a pair-occupation nature of copper. Calculated bond lengths, vibrational modes, ionization potentials, and dissociation energies for the smallest clusters agree very well with the available experimental information. A 1-D limit is rapidly reached by a chain system of 15 atoms. Most of the analyzed properties show substantial differences between the end atoms and those occupying central locations. The chain central atoms, with largest coordination numbers, bear the highest negative charge in the linear chains, and the same feature is observed in planar and 3-D structures. A semiempirical expression dependent on the cluster average coordination number is used to investigate the connection between the calculated cluster ionization potential and the local work function. The study confirms the validity of the cluster approach to improve the understanding of physicochemical properties at interfaces. * Corresponding authors. Fax: (803)-777-8265.
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.
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.
Journal of Nanoparticle Research, 2012
We present ab-initio density-functional calculations of the structural, magnetic, and chemical properties of cobalt-copper clusters (1 nm in size) with two to six atoms. We applied several search methods to find the most stable configurations for all stoichiometries. Particular attention is given to the relation between the geometric and magnetic structures. The clusters behavior is basically governed by the Co-Co interaction and to a lesser extent by the Co-Cu and Cu-Cu interactions. A tendency for Co-clumping is observed. Such information is quite relevant for segregation processes found in bulk Co-Cu alloys. For a given cluster size, magnetic moments increase mostly by 2l B per Co-substitution coming from the cobalt d-states, while for some cases s-electrons give rise to itinerant magnetism. Magnetic moment results are also consistent with the ultimate jellium model because of a 2D to 3D geometrical transition. The chemical potential indicates less chemical stability with the Co atoms, while the molecular hardness can be linked mostly to the ionization potential for these small clusters.
DFT study of electronic structure and geometry of anionic copper clusters< span>< img height
2008
Based on both total energy calculations and comparison of experimental and calculated characteristics of photoelectron spectra (PHES), the structural assignment of Cu À 11 , Cu À 12 and Cu À 13 clusters has been made using DFT model with previously developed S2LYP functional. In case of Cu À 13 cluster our decisions were also based on similarity of the geometries of copper and sodium clusters. The calculated characteristics of PHES for all the assigned structures are in excellent agreement with the experimental ones. The assigned geometries of Cu À 11 and Cu À 12 have been compared with those of recently established structures of silver clusters, which turned out to be very similar. In the meantime, the structure of the most stable Cu À 13 cluster is significantly distorted in comparison with the structure of Na À 13 cluster.
The Journal of Chemical Physics, 2002
In this paper we study nine neutral copper clusters through the theoretical characterization of their molecular structures, binding energy, electronic properties, and reactivity descriptors. Geometry optimization and vibrational analysis were performed using density functional theory calculations with a hybrid functional combined with effective core potentials. It is shown that reactivity descriptors combined with reactivity principles like the minimum polarizability and maximum hardness are operative for characterizing and rationalizing the electronic properties of copper clusters.