Summary Abstract: Electron density functional approach to surface segregation in binary solid solutions

1985 ◽  
Vol 3 (3) ◽  
pp. 817-818
Author(s):  
H. Yamauchi
Keyword(s):  
Electron Density ◽  
Solid Solutions ◽  
Density Functional ◽  
Surface Segregation ◽  
Functional Approach

scholarly journals Phase separation and surface segregation in ceria–zirconia solid solutions

2011 ◽  
Vol 467 (2131) ◽  
pp. 1925-1938 ◽  
Author(s):  
Ricardo Grau-Crespo ◽  
Nora H. de Leeuw ◽  
Said Hamad ◽  
Umesh V. Waghmare
Keyword(s):  
Phase Separation ◽  
High Temperatures ◽  
Solid Solutions ◽  
Density Functional ◽  
Surface Segregation ◽  
Equilibrium Concentration ◽  
Density Functional Theory Calculations ◽  
Atomic Scale ◽  
Functional Theory ◽  
Wide Range

Using a combination of density functional theory calculations and statistical mechanics, we show that a wide range of intermediate compositions of ceria–zirconia solid solutions are thermodynamically metastable with respect to phase separation into Ce-rich and Zr-rich oxides. We estimate that the maximum equilibrium concentration of Zr in CeO 2 at 1373 K is approximately 2 per cent, and therefore, equilibrated samples with higher Zr content are expected to exhibit heterogeneity at the atomic scale. We also demonstrate that in the vicinity of the (111) surface, cation redistribution at high temperatures will occur with significant Ce enrichment of the surface, which we attribute to the more covalent character of Zr–O bonds compared with Ce–O bonds. Although the kinetic barriers for cation diffusion normally prevent the decomposition/segregation of ceria–zirconia solid solutions in typical catalytic applications, the separation behaviour described here can be expected to occur in modern three-way catalytic converters, where very high temperatures are reached.

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.

Understanding the molecular mechanism of the stereoselective conversion of N-trialkylsilyloxy nitronates into bicyclic isoxazoline derivatives

2021 ◽  
Author(s):  
Agnieszka Kącka-Zych ◽  
Radomir Jasinski
Keyword(s):  
Density Functional Theory ◽  
Molecular Mechanism ◽  
Electron Density ◽  
Density Functional ◽  
Dft Method ◽  
Functional Theory ◽  
Molecular Electron ◽  
Molecular Electron Density Theory

Conversion of N-trialkylsilyloxy nitronates into bicyclic isoxazoline derivatives has been explored using Density Functional Theory (DFT) method within the context of the Molecular Electron Density Theory (MEDT) at the B97XD(PCM)/6-311G(d,p)...

Developing orbital-free quantum crystallography: the local potentials and associated partial charge densities

2021 ◽  
Vol 77 (4) ◽  
Author(s):  
Vladimir Tsirelson ◽  
Adam Stash
Keyword(s):  
Density Functional Theory ◽  
Electron Density ◽  
Density Functional ◽  
Electronic Energy ◽  
Physical Content ◽  
Functional Theory ◽  
Orbital Free ◽  
The One ◽  
Physical And Chemical ◽  
Quantum Crystallography

This work extends the orbital-free density functional theory to the field of quantum crystallography. The total electronic energy is decomposed into electrostatic, exchange, Weizsacker and Pauli components on the basis of physically grounded arguments. Then, the one-electron Euler equation is re-written through corresponding potentials, which have clear physical and chemical meaning. Partial electron densities related with these potentials by the Poisson equation are also defined. All these functions were analyzed from viewpoint of their physical content and limits of applicability. Then, they were expressed in terms of experimental electron density and its derivatives using the orbital-free density functional theory approximations, and applied to the study of chemical bonding in a heteromolecular crystal of ammonium hydrooxalate oxalic acid dihydrate. It is demonstrated that this approach allows the electron density to be decomposed into physically meaningful components associated with electrostatics, exchange, and spin-independent wave properties of electrons or with their combinations in a crystal. Therefore, the bonding information about a crystal that was previously unavailable for X-ray diffraction analysis can be now obtained.

Sign in / Sign up

Export Citation Format

Share Document