Core-hole effect in the one-particle approximation revisited from density functional theory

2009 ◽  
Vol 79 (23) ◽  
Author(s):  
Vincent Mauchamp ◽  
Michel Jaouen ◽  
Peter Schattschneider
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Core Hole ◽  
Functional Theory ◽  
The One ◽  
Hole Effect ◽  
Particle Approximation

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.

The one-electron self-interaction error in 74 density functional approximations: a case study on hydrogenic mono- and dinuclear systems

2020 ◽  
Vol 22 (28) ◽  
pp. 15805-15830 ◽  
Author(s):  
Dale R. Lonsdale ◽  
Lars Goerigk
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Model Systems ◽  
Electron Model ◽  
Functional Theory ◽  
The One

The one-electron self-interaction error (SIE) is analysed for 74 Density Functional Theory (DFT) approximations in a series of novel one-electron model systems revealing new aspects of the SIE that should be considered in future DFT developments.

scholarly journals Density functional theory (DFT) calculations of conformational energies and interconversion pathways in 1,2,7-thiadiazepane

2011 ◽  
Vol 76 (3) ◽  
pp. 395-406 ◽  
Author(s):  
Mina Haghdadi ◽  
Nahid Farokhi
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Density Functional ◽  
Activation Barrier ◽  
Stable Conformer ◽  
Functional Theory ◽  
Conformational Interconversion ◽  
Interconversion Barrier ◽  
The One ◽  
Twist Boat

The molecular structure and conformational analysis of 1,2,7-thiadiazapane conformers were investigated by density functional theory (DFT) calculations at the B3LYP/cc-pVDZ level of theory. Four twist-chair (TC), six twist-boat (TB), two boat (B), two chair (C) and four twist (T) conformers were identified as minima and transition states for 1,2,7-thiadiazepane. The TC1 conformer is the most stable conformer and the twist-chair conformers are predicted to be lower in energy than their corresponding boat and chair conformations. DFT predicts a small barrier to pseudo-rotation and a remarkable activation barrier for the conformational interconversion of the twist-chair conformers to their corresponding boat conformers. The simplest conformational process and the one with the lowest barrier is the degenerate interconversion of the twist-chair 3 (TC3) conformation with itself via the CS symmetric chair (C2) transition state. The calculated strain energy barrier for this process is 2.41 kJ mol-1. The highest conformational interconversion barrier is between TC2 and twistboat 3 (TB3) forms, which was found to be 75.62 kJ mol-1.

Aromaticity in pericondensed cyclopenta-fused polycyclic aromatic hydrocarbons determined by density functional theory nucleus-independent chemical shifts and the Y-rule — Implications in oil asphaltene stability

2009 ◽  
Vol 87 (10) ◽  
pp. 1280-1295 ◽  
Author(s):  
Yosadara Ruiz-Morales
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Stability ◽  
Density Functional ◽  
Chemical Shifts ◽  
Functional Theory ◽  
Electronic Distribution ◽  
Polycyclic Aromatic ◽  
Minimum Number ◽  
The Stability ◽  
The One

The characterization of the stability of the fused aromatic region (FAR) in oil asphaltenes in terms of kinetic and thermodynamic stability is primary. Such an understanding is important if we are to get the optimal use from the heavy fraction of any crude oil. The FAR region is composed of pericondensed cyclopenta-fused polycyclic aromatic hydrocarbon compounds (CPPAHs) with N, S, and O heteroatoms. The Clar model, which states that the most important representation of a PAH is one having the maximum number of disjoint π-sextets, depicted by inscribed circles, and a minimum number of fixed double bonds, captures the essence of the kinetic and thermodynamic stability arguments. This model is readily employed for complex aromatics of the sort to be considered for asphaltenes. In the present research we prove that the aromaticity of CPPAHs can be assessed by using the qualitative easy-to-apply Y-rule. In the literature, it is proven that the Y-rule is applicable to elucidate the aromaticity of benzenoid PAHs and it has been validated for pericondensed benzenoid PAHs but not for pericondensed CPPAHs. Here, we verify that it is applicable for CPPAHs. The applicability of the Y-rule has been theoretically proven by comparing the π-electronic distribution obtained with it with the one obtained from nucleus-independent chemical shift (NICS) calculations at the density functional theory (DFT) level. The importance of doing this is that due to the polydispersity in the composition of the oil asphaltenes, and to understand their aromatic core structure, it is necessary to be able to asses the aromaticity of many cyclopenta-fused PAHs (possibly more than 500), of different sizes (up to 15 rings between hexagons and pentagons), and different spatial rearrangements in a quick but realistic and effective way. To try to do this with NICS will be very time consuming and computationally expensive, especially in the case of big systems.

Simulations of krypton matrix effects on the electronic spectrum of Na2

1994 ◽  
Vol 72 (11-12) ◽  
pp. 909-912 ◽  
Author(s):  
A. V. Nemukhin ◽  
B. L. Grigorenko ◽  
G. B. Sergeev
Keyword(s):  
Molecular Dynamics ◽  
Density Functional Theory ◽  
Small Molecules ◽  
Density Functional ◽  
Matrix Effects ◽  
Opposite Sign ◽  
Functional Theory ◽  
Spectral Shifts ◽  
The One ◽  
Dynamics Simulations

A model for calculation of spectral shifts in small molecules due to matrix environments is developed. The approach is based on the one-electron approximation and combines methods of ab initio quantum chemistry, density functional theory, and molecular dynamics simulations. Applications to Na2Kr62 heteroclusters demonstrate that the model is capable of reproducing spectral shifts of opposite sign for the experimentally studied A–X and B–X transitions in Na2 trapped inside the Kr matrix.

Investigation of structural and energetic behavior of 55-atom Pt–Ag–Au ternary nanoalloys

2021 ◽  
pp. 2150174
Author(s):  
Hüseyin Yıldırım ◽  
Ali Kemal Garip
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Energy Analysis ◽  
Many Body ◽  
Functional Theory ◽  
Mixing Energy ◽  
Chemical Ordering ◽  
The One ◽  
Body Potential ◽  
Basin Hopping

A systematic theoretical investigation of structural and energetic behaviors of 55-atom Pt–Ag–Au ternary nanoalloys has been performed in two different composition systems. We have performed Gupta and Density Functional Theory (DFT) approaches on chosen systems. The Basin-Hopping algorithm is used for structural optimizations of PtnAg[Formula: see text]Au[Formula: see text] ([Formula: see text]–13) and PtnAu[Formula: see text]Ag[Formula: see text] ([Formula: see text]–13) ternary nanoalloys with Gupta many-body potential to model interatomic interactions. Local optimization results show that while the tendency of Au atoms to be located varies according to the composition system, the tendency of Pt and Ag atoms to be located does not change in both. For all compositions of Pt–Ag–Au nanoalloys, the structures with the best chemical ordering were then reoptimized by DFT relaxations and the mixing energies of the Gupta and DFT levels were compared. Our mixing energy analysis showed that PtnAg[Formula: see text]Au[Formula: see text] ([Formula: see text]–13) nanoalloys are not energetically suitable for mixing at both Gupta and DFT level. Also, mixing energy variations of PtnAu[Formula: see text]Ag[Formula: see text] ([Formula: see text]–13) nanoalloys obtained at Gupta level does not agree with the one obtained at DFT level. In addition, it has been found that the minimization energy changes when an atom in the central site is exchanging by an atom in the second shell and surface.

Sign in / Sign up

Export Citation Format

Share Document