Misleading evidence for covalent bonding from EuIIIX and AmIIIX density functional theory bond lengths

2014 ◽  
Vol 194 ◽  
pp. 8-13 ◽  
Author(s):  
Michael Dolg ◽  
Xiaoyan Cao ◽  
Jan Ciupka
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Covalent Bonding ◽  
Functional Theory ◽  
Bond Lengths ◽  
Misleading Evidence

scholarly journals Influence of Copper(I) Halides on the Reactivity of Aliphatic Carbodiimides

2020 ◽  
Vol 3 (1) ◽  
pp. 20
Author(s):  
Valentina Ferraro ◽  
Marco Bortoluzzi
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
General Formula ◽  
Electron Density ◽  
Density Functional ◽  
Functional Theory ◽  
Fukui Functions ◽  
Bond Lengths ◽  
Linear Complexes ◽  
Nitrogen Bond

The influence of copper(I) halides CuX (X = Cl, Br, I) on the electronic structure of N,N′-diisopropylcarbodiimide (DICDI) and N,N′-dicyclohexylcarbodiimide (DCC) was investigated by means of computational DFT (density functional theory) methods. The coordination of the considered carbodiimides occurs by one of the nitrogen atoms, with the formation of linear complexes having a general formula of [CuX(carbodiimide)]. Besides varying the carbon–nitrogen bond lengths, the thermodynamically favourable interaction with Cu(I) reduces the electron density on the carbodiimides and alters the energies of the (NCN)-centred, unoccupied orbitals. A small dependence of these effects on the choice of the halide was observable. The computed Fukui functions suggested negligible interaction of Cu(I) with incoming nucleophiles, and the reactivity of carbodiimides was altered by coordination mainly because of the increased electrophilicity of the {NCN} fragments.

6-Bromoindigo dye

2012 ◽  
Vol 68 (4) ◽  
pp. o160-o163 ◽  
Author(s):  
David J. Szalda ◽  
Keith Ramig ◽  
Olga Lavinda ◽  
Zvi C. Koren ◽  
Lou Massa
Keyword(s):  
Density Functional Theory ◽  
Quantum Theory ◽  
Hydrogen Bonds ◽  
Density Functional ◽  
Stacking Interactions ◽  
Inversion Center ◽  
Asymmetric Unit ◽  
Functional Theory ◽  
Bond Lengths ◽  
Type C

6-Bromoindigo (MBI) [systematic name: 6-bromo-2-(3-oxo-2,3-dihydro-1H-indol-2-ylidene)-2,3-dihydro-1H-indol-3-one], C16H9BrN2O2, crystallizes with one disordered molecule in the asymmetric unit about a pseudo-inversion center, as shown by the Br-atom disorder of 0.682 (3):0.318 (3). The 18 indigo ring atoms occupy two sites which are displaced by 0.34 Å from each other as a result of this packing disorder. This difference in occupancy factors results in each atom in the reported model used to represent the two disordered sites being 0.08 Å from the higher-occupancy site and 0.26 Å from the lower-occupancy site. Thus, as a result of the disorder, the C—Br bond lengths in the disordered components are 0.08 and 0.26 Å shorter than those found in 6,6′-dibromoindigo (DBI) [Süsse & Krampe (1979).Naturwissenschaften,66, 110], although the distances within the indigo ring are similar to those found in DBI. The crystals are also twinned by merohedry. Stacking interactions and hydrogen bonds are similar to those found in the structures of indigo and DBI. In MBI, an interaction of the type C—Br...C replaces the C—Br...Br interactions found in DBI. The interactions in MBI were calculated quantum mechanically using density functional theory and the quantum theory of atoms in molecules.

Ultrathin oxide films: CaO layers on BaO and SrO

2008 ◽  
Vol 1148 ◽  
Author(s):  
Chris E Mohn ◽  
Neil L. Allan ◽  
John H. Harding
Keyword(s):  
Density Functional Theory ◽  
Atomistic Simulation ◽  
Density Functional ◽  
Functional Theory ◽  
Bond Lengths ◽  
Simulation Techniques ◽  
Ultrathin Oxide Films ◽  
Anion Separation ◽  
Crystalline Oxides ◽  
Ultrathin Oxide

AbstractPrompted by renewed interest in the crystalline oxides-on-semiconductors interface, periodic density functional theory and atomistic simulation techniques are used to examine the formation of a layer of CaO on a BaO substrate. We examine how CaO islands which form at coverages less than 100% adjust to the substrate in which the cation-anion separation is substantially larger than in CaO itself. All Ca-O bond lengths in the island are shorter than that in bulk CaO. Corner O atoms in the islands are associated with particularly short Ca-O bond lengths, and the shape of the islands is dominated by (100) edges. Once formed, islands with intact edges will remain intact. Interactions between islands at larger coverages are also investigated and we see the formation of characteristic elliptical gaps and loops.

First-principles study of oxygen and hydrogen adsorption on Pt(111) and PtML/Pd(111) surfaces

2015 ◽  
Vol 29 (31) ◽  
pp. 1550199 ◽  
Author(s):  
J. L. Nie ◽  
L. Ao ◽  
X. T. Zu
Keyword(s):  
Density Functional Theory ◽  
First Principles ◽  
Density Functional ◽  
Hydrogen Adsorption ◽  
Chemical Interaction ◽  
Energy Difference ◽  
Covalent Bonding ◽  
Oxygen Molecule ◽  
First Principles Calculations ◽  
Functional Theory

In this paper, first-principles calculations based on density functional theory (DFT) have been performed to investigate the adsorption of oxygen and hydrogen on [Formula: see text] and [Formula: see text] surfaces covered by monolayer (ML) of [Formula: see text]. The results have shown that the oxygen molecule tends to adsorb on fcc site on both surfaces at the coverage of 0.25 ML, which becomes degeneration with hcp site when the coverage increases to 1 ML. For both oxygen and hydrogen, the adsorption on [Formula: see text] surface are stronger than those on [Formula: see text] surface. The adsorption energy difference for oxygen on the two surfaces is [Formula: see text][Formula: see text]0.2 eV at the coverage of 1 ML, which increases to [Formula: see text][Formula: see text]0.6 eV with the coverage decreasing to 0.25 ML. The similar energy difference was also found for hydrogen adsorption. The density of states analysis have demonstrated the chemical interaction of adsorbed oxygen with both pure [Formula: see text] and [Formula: see text] surfaces with certain shift of [Formula: see text] states to lower level compared to isolated oxygen. For hydrogen adsorption, the hybridization of [Formula: see text] with [Formula: see text] states were observed for both surfaces, indicating the covalent bonding component of H–Pt bond.

Ab Initio Calculations of Electronic and Magnetic Properties of AlMnO3 Perovskite Manganites

2015 ◽  
Vol 754-755 ◽  
pp. 757-761
Author(s):  
Abdullah Chik ◽  
S. Saad ◽  
Cheow Keat Yeoh ◽  
R.M. Zaki ◽  
F. Che Pa
Keyword(s):  
Density Functional Theory ◽  
Magnetic Properties ◽  
Electronic Structure ◽  
Ground State ◽  
Density Functional ◽  
Covalent Bonding ◽  
Perovskite Manganites ◽  
Functional Theory ◽  
Cubic Crystal ◽  
Energy Approximation

The electronic structure of the perovskite manganites AlMnO3cubic crystal was presented. The calculations were made within density functional theory and PBE exchange correlations energy approximation. It was found that the crystal exhibit covalent bonding between Mn and O with superexchange mechanism. At groundstate, AlMnO3stabilizes in antiferromagnetic structure with semi metallic like nature at the ground state.

scholarly journals Density Functional Theory Investigation of the Doping Effects of Bromine and Fluorine on the Electronic and Optical Properties of Neutral and Ionic Perylene

2021 ◽  
pp. 1-13
Author(s):  
Auwal A. Abubakar ◽  
A. B. Suleiman ◽  
A. S. Gidado
Keyword(s):  
Density Functional Theory ◽  
Optical Properties ◽  
Density Functional ◽  
Energy Gap ◽  
Chemical Hardness ◽  
Functional Theory ◽  
Bond Lengths ◽  
Hybrid Molecules ◽  
Non Linear ◽  
Linear Optical Properties

Perylene and its derivatives are some of the promising organic semiconductors. They have found vast applications in many areas such as photovoltaic systems, organic light-emitting diodes, and so on. The instability of organic molecules under ambient conditions is one factor deterring the commercialization of organic semiconductor devices. Currently, most of the investigation of Perylene and its derivatives concentrated on its diimide and bisimide derivatives. In this work, an investigation of the effects of doping Bromine and Fluorine on the electronic and non-linear optical properties was carried out based on Density Functional Theory (DFT) as implemented in the Gaussian 09 software package. We computed the Molecular geometries of the molecules, HOMO-LUMO energy gap, global chemical indices and non-linear optical properties using the same method. The bond lengths and angles of the mono-halogenated molecules at different charge states were found to be less than that of the isolated Perylene. 1-fluoroperylene was found to be the most stable amongst the studied molecule for having the least bond angles and bond lengths. In the calculation of the energy bandgap neutral 1-fluoroperylene was observed to have the highest energy gap 3.0414 eV and 3.0507 eV for 6-31++G(d,p) and 6-311++G(d,p) basis sets respectively. These results were found to agree with the existing literature. This reconfirmed 1-fluoroperylene as the most stable molecule. The computations of the ionic molecules reported small values of the energy gap. The molecule with the most chemical hardness was obtained to be the neutral 1-fluoroperylene with a chemical hardness of 1.5253eV. All the ionic molecules results were found to be more reactive than their neutral form for having lower values of chemical hardness. For NLO calculations, the results showed an increment in their values with the ionic hybrid molecules having the largest values.  In the case of first-order hyper-polarizability, 1-bromoperylene (neutral), 1-fluoroperylene (neutral), 1-bromoperylene (anionic), 1-fluoroperylene (anionic), 1-bromoperylene (cationic) and 1-fluoroperylene (cationic) were found to be 73.93%, 1.71%, 83.9%, 39.2%,38.7% and 41.7% larger than that of Urea respectively. These calculated results make these hybrid molecules suitable for a wide range of optoelectronic applications.

Structural and Electronic Properties of Pt3 and Pt3M Clusters (M=Au, Ag, Sn, Fe)

2012 ◽  
Vol 463-464 ◽  
pp. 143-146
Author(s):  
Dong Mei Li
Keyword(s):  
Density Functional Theory ◽  
Energy Level ◽  
Electronic Properties ◽  
Density Functional ◽  
Functional Theory ◽  
Bond Lengths ◽  
Energy Gaps ◽  
Structural And Electronic Properties ◽  
Good For ◽  
Atom Energy

With density functional theory, the structural and electronic properties of Pt3 and Pt3M clusters (M=Au, Ag, Sn, Fe) have been studied. It is found that all the Pt3M clusters show planar and tetrahedral structures and their Pt-Pt bond lengths are larger than the bond lengths of Pt3. The effect of M doping on electronic properties of Pt3 clusters have been investigated. It is found that by adding one M atom, energy gaps of the corresponding clusters become smaller. The calculated results also indicate that M atom makes the highest energy level of Pt atoms shift highly, except for tetrahedral Pt3Au clusters. These may be good for analyzing adsorption problems

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