Electronic Structures and Spin Density Distributions of BrO2and (HO)2BrO Radicals. Mechanisms for Avoidance of Hypervalency and for Spin Delocalization and Spin Polarization

2013 ◽  
Vol 52 (20) ◽  
pp. 11806-11820 ◽  
Author(s):  
Rainer Glaser ◽  
Cory Camasta
Keyword(s):  
Spin Density ◽  
Spin Polarization ◽  
Electronic Structures ◽  
Density Distributions ◽  
Spin Delocalization

MAGNETIC COUPLING CONSTANTS AND SPIN DENSITY DISTRIBUTIONS FOR CYANO-BRIDGED Gd(III)-Fe(III) AND Gd(III)-Cr(III) COMPOUNDS: BROKEN-SYMMETRY AND DENSITY FUNCTIONAL THEORY CALCULATIONS

2005 ◽  
Vol 19 (15n17) ◽  
pp. 2538-2543 ◽  
Author(s):  
YI QUAN ZHANG ◽  
CHENG LIN LUO ◽  
ZHI YU
Keyword(s):  
Density Functional Theory ◽  
Spin Density ◽  
Spin Polarization ◽  
Density Functional ◽  
Population Analysis ◽  
Magnetic Coupling ◽  
Coupling Constants ◽  
Broken Symmetry ◽  
Functional Theory ◽  
Density Distributions

Magnetic coupling constants J for the complete structures of [ Gd(capro) 2( H 2 O )4 Cr(CN) 6]• H 2 O (capro represents caprolactam) (a) and trans-[ Fe(CN) 4(μ- CN )2 Gd ( H 2 O )4 (bpy) ]•4 H 2 O •1.5 bpy (b) have been calculated using hybrid density functional theory (DFT) B3LYP combined with a modified broken symmetry approach (BS). The calculated J value of -0.24 cm-1 for a is very close to the experimental -0.33 cm-1. They both show the antiferromagnetic interaction between Gd(III) and Cr(III) . For b, although the sign of the calculated J value of 4.24 cm-1 is different from that of the experimental -0.38 cm-1, the two values both show the weak magnetic coupling interaction between Gd(III) and Fe(III) . The spin density distributions are discussed on the basis of Mulliken population analysis. For complexes a and b, both transition metal ( Fe(III) or Cr(III) ) and rare earth Gd(III) display a spin polarization effect on the surrounding atoms, where a counteraction of the opposite polarization effects leads to a low spin density on the bridging ligand C1N1 . For the compounds Gd(III) - Cr(III) (a) and Gd(III) - Fe(III) (b) in the HS states, Cr(III) has stronger spin polarization influence on the bridging atoms than Fe(III) even causing the positive spin population on the bridging atom N1 .

scholarly journals Insights on spin delocalization and spin polarization mechanisms in crystals of azido copper(II) dinuclear complexes through the electron spin density Source Function

2017 ◽  
Vol 73 (4) ◽  
pp. 565-583 ◽  
Author(s):  
Carlo Gatti ◽  
Giovanni Macetti ◽  
Leonardo Lo Presti
Keyword(s):  
Spin Density ◽  
Spin Polarization ◽  
Source Function ◽  
Reference Points ◽  
Dinuclear Complexes ◽  
Azido Group ◽  
Local Spin ◽  
Whole Space ◽  
Spin Delocalization ◽  
Spin Densities

The Source Function (SF) tool was applied to the analysis of thetheoreticalspin density in azido CuIIdinuclear complexes, where the azido group, acting as a coupler between the CuIIcations, is linked to the metal centres either in an end-on or in an end–end fashion. Results for only the former structural arrangement are reported in the present paper. The SF highlights to which extent the magnetic centres contribute to determine the local spin delocalization and polarization at any point in the dimetallic complex and whether an atom or group of atoms of the ligands act in favour or against a given local spin delocalization/polarization. Ball-and-stick atomic SF percentage representations allow for a visualization of the magnetic pathways and of the specific role played by each atom along these paths, at given reference points. Decomposition of SF contributions in terms of a magnetic and of a relaxation component provides further insight. Reconstruction of partial spin densities by means of the Source Function has for the first time been introduced. At variance with the standard SF percentage representations, such reconstructions offer a simultaneous view of the sources originating from specific subsets of contributing atoms, in a selected molecular plane or in the whole space, and are therefore particularly informative. The SF tool is also used to evaluate the accuracy of the analysed spin densities. It is found that those obtained at the unrestricted B3LYP DFT level, relative to those computed at the CASSCF(6,6) level, greatly overestimate spin delocalization to the ligands, but comparatively underestimate magnetic connection (spin transmission) among atoms, along the magnetic pathways. As a consequence of its excessive spin delocalization, the UB3LYP method also overestimates spin polarization mechanisms between the paramagnetic centres and the ligands. Spin delocalization measures derived from the refinement of Polarized Neutron Diffraction data seem in general superior to those obtained through the DFT UB3LYP approach and closer to the far more accurate CASSCF results. It is also shown that a visual agreement on the spin-resolved electron densities ραand ρβderived from different approaches does not warrant a corresponding agreement between their associated spin densities.

Salts of Ferricinium Cation and its Homologues: NMR Investigation, II EPR and NMR Spectra of sym-Polymethyl Substituted Ferricinium Cations

1980 ◽  
Vol 35 (11) ◽  
pp. 1415-1419 ◽  
Author(s):  
R. B. Materikova ◽  
V. N. Babin ◽  
S. P. Solodovnikov ◽  
I. R. Lyatifov ◽  
P. V. Petrovsky ◽  
...  
Keyword(s):  
Density Distribution ◽  
Spin Density ◽  
Spin Polarization ◽  
Nmr Spectra ◽  
General Pattern ◽  
Spin Density Distribution ◽  
Determining Factors ◽  
Spin Delocalization ◽  
C Nmr

Abstract The EPR, 1H and 13C NMR spectra of methylferricinium hexafluorophosphates, [(MenCp)2Fe]PF6, n = 0-5, have been recorded. HFS constants have been estimated for all the ligand atoms. The general pattern of the spin density distribution is shown to depend on the superposition of the various mechanisms of spin delocalization. For the majority of the cations the determining factors has been found to be represented by spin polarization over the π-skeleton.

Computational Investigation of the Asymmetry in Photosynthetic Reaction Center Models from First Principles

2020 ◽  
Author(s):  
Denis Artiukhin ◽  
Patrick Eschenbach ◽  
Johannes Neugebauer
Keyword(s):  
Spin Density ◽  
Reaction Center ◽  
Density Functional ◽  
Photosynthetic Reaction Center ◽  
Chem Phys ◽  
Molecular Structures ◽  
Error Characteristic ◽  
Molecular Systems ◽  
Density Distributions ◽  
The Asymmetry

We present a computational analysis of the asymmetry in reaction center models of photosystem I, photosystem II, and bacteria from <i>Synechococcus elongatus</i>, <i>Thermococcus vulcanus</i>, and <i>Rhodobacter sphaeroides</i>, respectively. The recently developed FDE-diab methodology [J. Chem. Phys., 148 (2018), 214104] allowed us to effectively avoid the spin-density overdelocalization error characteristic for standard Kohn–Sham Density Functional Theory and to reliably calculate spin-density distributions and electronic couplings for a number of molecular systems ranging from dimeric models in vacuum to large protein including up to about 2000 atoms. The calculated spin densities showed a good agreement with available experimental results and were used to validate reaction center models reported in the literature. We demonstrated that the applied theoretical approach is very sensitive to changes in molecular structures and relative orientation of molecules. This makes FDE-diab a valuable tool for electronic structure calculations of large photosynthetic models effectively complementing the existing experimental techniques.

scholarly journals Spin Polarization Properties of Pentagonal PdSe2 Induced by 3D Transition-Metal Doping: First-Principles Calculations

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2339 ◽  
Author(s):  
Xiuwen Zhao ◽  
Bin Qiu ◽  
Guichao Hu ◽  
Weiwei Yue ◽  
Junfeng Ren ◽  
...  
Keyword(s):  
Transition Metal ◽  
Spin Polarization ◽  
First Principles ◽  
Magnetic Moments ◽  
First Principles Calculations ◽  
Density Distributions ◽  
Metal Atoms ◽  
Transition Metal Atoms ◽  
Theoretical Investigations ◽  
Densities Of States

The electronic structure and spin polarization properties of pentagonal structure PdSe2 doped with transition metal atoms are studied through first- principles calculations. The theoretical investigations show that the band gap of the PdSe2 monolayer decreases after introducing Cr, Mn, Fe and Co dopants. The projected densities of states show that p-d orbital couplings between the transition metal atoms and PdSe2 generate new spin nondegenerate states near the Fermi level which make the system spin polarized. The calculated magnetic moments, spin density distributions and charge transfer of the systems suggest that the spin polarization in Cr-doped PdSe2 will be the biggest. Our work shows that the properties of PdSe2 can be modified by doping transition metal atoms, which provides opportunity for the applications of PdSe2 in electronics and spintronics.

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