scholarly journals Role of Hemibonding in the Structure and Ultraviolet Spectroscopy of the Aqueous Hydroxyl Radical

2020 ◽  
Author(s):  
Bhaskar Rana ◽  
John Herbert
Keyword(s):  
Density Functional Theory ◽  
Absorption Spectrum ◽  
Hydroxyl Radical ◽  
Density Functional ◽  
Finite Size ◽  
Ultraviolet Absorption Spectrum ◽  
Absorption Feature ◽  
Generalized Gradient ◽  
Functional Theory ◽  
A Minor

The presence of a hemibond in the local solvation structure of the aqueous hydroxyl radical has long been debated, as its appearance in <i>ab initio</i> simulations based on density functional theory is sensitive to self-interaction error (favoring a two-center, three-electron hemibond) but also to finite-size effects. Simulations reported here use a mixed quantum mechanics/molecular mechanics (QM/MM) framework in a very large periodic simulation cell, in order to avoid finite-size artifacts and to facilitate testing of various density functionals, in order to probe the effects of delocalization error. The preponderance of hemibonded structures predicted by generalized gradient approximations persists in simulations using the hybrid functionals B3LYP and PBE0, but is reduced to a minor population if the fraction of exact exchange is increased significantly. The hemibonded population is also small in simulations employing the long-range corrected functional LRC-wPBE. Electronic spectra are computed using time-dependent density functional theory, and from these calculations emerges a consensus picture in which hemibonded configurations play an outsized role in the absorption spectrum, even when present as a minority species. An intense 1b<sub>2</sub> (H<sub>2</sub>O) --> 2p (OH) charge-transfer transition in hemibonded configuration of the radical proves to be responsible for an absorption feature at 230~nm that is strongly shifted with respect to the gas-phase absorption at 307 nm, but this intense feature is substantially diminished in aqueous geometries where the hemibond is absent. Although not yet sufficient to quantitatively establish the population of hemibonded OH(aq), these simulations do suggest that its presence is revealed by the strongly shifted ultraviolet absorption spectrum of the aqueous radical.<br>

scholarly journals Role of Hemibonding in the Structure and Ultraviolet Spectroscopy of the Aqueous Hydroxyl Radical

2020 ◽  
Author(s):  
Bhaskar Rana ◽  
John Herbert
Keyword(s):  
Density Functional Theory ◽  
Absorption Spectrum ◽  
Hydroxyl Radical ◽  
Density Functional ◽  
Finite Size ◽  
Ultraviolet Absorption Spectrum ◽  
Absorption Feature ◽  
Generalized Gradient ◽  
Functional Theory ◽  
A Minor

The presence of a hemibond in the local solvation structure of the aqueous hydroxyl radical has long been debated, as its appearance in <i>ab initio</i> simulations based on density functional theory is sensitive to self-interaction error (favoring a two-center, three-electron hemibond) but also to finite-size effects. Simulations reported here use a mixed quantum mechanics/molecular mechanics (QM/MM) framework in a very large periodic simulation cell, in order to avoid finite-size artifacts and to facilitate testing of various density functionals, in order to probe the effects of delocalization error. The preponderance of hemibonded structures predicted by generalized gradient approximations persists in simulations using the hybrid functionals B3LYP and PBE0, but is reduced to a minor population if the fraction of exact exchange is increased significantly. The hemibonded population is also small in simulations employing the long-range corrected functional LRC-wPBE. Electronic spectra are computed using time-dependent density functional theory, and from these calculations emerges a consensus picture in which hemibonded configurations play an outsized role in the absorption spectrum, even when present as a minority species. An intense 1b<sub>2</sub> (H<sub>2</sub>O) --> 2p (OH) charge-transfer transition in hemibonded configuration of the radical proves to be responsible for an absorption feature at 230~nm that is strongly shifted with respect to the gas-phase absorption at 307 nm, but this intense feature is substantially diminished in aqueous geometries where the hemibond is absent. Although not yet sufficient to quantitatively establish the population of hemibonded OH(aq), these simulations do suggest that its presence is revealed by the strongly shifted ultraviolet absorption spectrum of the aqueous radical.<br>

Dissociation of dinitrogen on iron clusters: A detailed study of the Fe16 + N2 case.

2020 ◽  
Author(s):  
Bole Chen ◽  
Gennady L. Gutsev ◽  
Weiguo Sun ◽  
Xiao-Yu Kuang ◽  
Cheng Lu ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Basis Set ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Iron Clusters ◽  
Generalized Gradient Approximation

The coalescence of two Fe8N as well as the structure of the Fe16N2 cluster were studied using density functional theory with the generalized gradient approximation and a basis set of...

An Investigation of Half-Metallic Ferromagnets Behavior in Hg2CuTi-Type Heusler Alloy Ti2FeAl by Using GGA

2012 ◽  
Vol 535-537 ◽  
pp. 1291-1294 ◽  
Author(s):  
Xiu De Yang ◽  
Bo Wu ◽  
Song Zhang
Keyword(s):  
Density Functional Theory ◽  
Heusler Alloy ◽  
Density Functional ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Half Metallic ◽  
Generalized Gradient Approximation ◽  
Indirect Exchange ◽  
The Density Functional Theory ◽  
Direct Hybridization

By using generalized gradient approximation (GGA) scheme within the density functional theory (DFT), the electronic and magnetic properties of Hg2CuTi-type Heusler alloy Ti2FeAl were investigated. The results reveal that a 100% spin polarization appears at Fermi level (εF) in Ti2FeAl, and is maintained during lattice range of 5.1Å~6.2Å. Ti2FeAl is one of stable Half-Metallic Ferromagnets (HMF) with a spin-minority gap of 0.5 eV at εF and total magnetic moment of 1μB per unit cell. Our studies also indicate that the competition between RKKY-type indirect exchange and direct hybridization of d-electronic atoms plays a dominating role in determining the magnetism.

Density Functional Theory Approach for Muon Sites Estimation in Mn3Sn

2021 ◽  
Vol 1028 ◽  
pp. 199-203
Author(s):  
Fiqhri Heda Murdaka ◽  
Edi Suprayoga ◽  
Abdul Muizz Pradipto ◽  
Kohji Nakamura ◽  
Agustinus Agung Nugroho
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Local Density ◽  
Full Potential ◽  
Theory Approach ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Electrostatic Potential Calculation ◽  
A Site ◽  
Linearized Augmented Plane Wave

We report the estimation of muon sites inside Mn3Sn using density functional theory based on the full-potential linearized augmented plane wave (FLAPW) calculation. Our calculation shows that the Perdew–Burke–Ernzerhof (PBE) Generalized-Gradient Approximation (GGA) functional is closer to the experimental structure compared to the von Barth-Hedin Local Density Approximation (LDA)-optimized geometry. The PBE GGA is therefore subsequently used in FLAPW post-calculation for the electrostatic potential calculation to find the local minima position as a guiding strategy for estimating the muon site. Our result reveals at least two muon sites of which one is placed at the center between two Mn-Sn triangular layers (A site) and the other at the trigonal prismatic site of Sn atom (B site). The total energy of Mn3Sn system in the presence of muon at A site or B site are compared and we find that A site is a more favorable site for muon to stop.

scholarly journals Density functional theory study of electronic properties of Bi2Se3 and Bi2Te3

2017 ◽  
Vol 12 (3) ◽  
Author(s):  
Abdullahi Lawal ◽  
Amiruddin Shaari
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Topological Insulators ◽  
Van Der Waals Interactions ◽  
Partial Density ◽  
Total Density ◽  
Density Of State ◽  
Generalized Gradient ◽  
Linear Dispersion ◽  
Functional Theory

Topological insulators are layered materials via van der Waals interactions with hexagonal unit cell similar to that of graphene. The exciting features of Bi2Se3 and Bi2Te3 topological insulators their zero band gap surface states exhibiting linear dispersion at the Fermi energy. We present here first principles study pertaining to electronics properties of Bi2Se3 and Bi2Te3 compound with and without spin-orbit interaction using density functional theory (DFT). Total density of state (DOS), partial density of state (PDOS) and band structure where determined by Quantum-Espresso simulation package which uses plane wave basis and pseudopotential for the core electrons, while treating exchange-correlation potential with generalized gradient approximation (GGA). From our computations, the obtained results were found to be consistent with the available experimental results. 

scholarly journals Structural, Electronic, and Magnetic Properties of Mn4N Perovskite: Density Functional Theory Calculations and Monte Carlo Study

2019 ◽  
Vol 33 (5) ◽  
pp. 1507-1512 ◽  
Author(s):  
A. Azouaoui ◽  
M. El Haoua ◽  
S. Salmi ◽  
A. El Grini ◽  
N. Benzakour ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Monte Carlo ◽  
Magnetic Properties ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Generalized Gradient ◽  
Critical Temperatures ◽  
Metallic Behavior ◽  
Functional Theory ◽  
Electronic And Magnetic Properties

AbstractIn this paper, we have studied the structural, electronic, and magnetic properties of the cubic perovskite system Mn4N using the first principles calculations based on density functional theory (DFT) with the generalized gradient approximation (GGA). The obtained data from DFT calculations are used as input data in Monte Carlo simulation with a mixed spin-5/2 and 1 Ising model to calculate the magnetic properties of this compound, such as the total, partial thermal magnetization, and the critical temperatures (TC). The obtained results show that Mn4N has a ferrimagnetic structure with two different sites of Mn in the lattice and presents a metallic behavior. The obtained TC is in good agreement with experimental results.

scholarly journals Electronic properties of the coronene series from thermally-assisted-occupation density functional theory

RSC Advances ◽  
2018 ◽  
Vol 8 (60) ◽  
pp. 34350-34358 ◽  
Author(s):  
Chia-Nan Yeh ◽  
Can Wu ◽  
Haibin Su ◽  
Jeng-Da Chai
Keyword(s):  
Density Functional Theory ◽  
Electronic Properties ◽  
Density Functional ◽  
Finite Size ◽  
Comprehensive Understanding ◽  
Functional Theory ◽  
Graphene Flakes

To fully utilize the great potential of graphene in electronics, a comprehensive understanding of the electronic properties of finite-size graphene flakes is essential.

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