AM1 Calculations of Spin Distribution in Hydroxyanthrasemiquinones

1995 ◽  
Vol 60 (7) ◽  
pp. 1081-1093 ◽  
Author(s):  
Martin Breza ◽  
Vlasta Brezová
Keyword(s):  
Experimental Data ◽  
Spin Density ◽  
Spin State ◽  
Epr Spectra ◽  
Am1 Method ◽  
Distribution Data ◽  
Am1 Calculations ◽  
Spin Distribution ◽  
Higher Spin

The AM1 method was used to obtain the optimum geometries of hydroxyanthrasemiquinones. The relation between the spin distribution data obtained by analysis of EPR spectra and by AM1 calculations depends on the position of the C atom within the aromatic skeleton, on its spin density sign and on its position relative to OH substituents. Complete annihilation of higher spin state contaminations is insufficient to eliminate the significant discrepancies between the theoretical and experimental data.

EPR spectra and defect states in glasses of the GexS100-x system

1982 ◽  
Vol 47 (7) ◽  
pp. 1787-1793 ◽  
Author(s):  
Miloslav Frumar ◽  
Gustáv Plesch ◽  
Eva Černošková ◽  
Václav Černý ◽  
Ladislav Tichý ◽  
...  
Keyword(s):  
Experimental Data ◽  
Epr Spectra ◽  
Defect States ◽  
Composition Region ◽  
Active Defect ◽  
Temperature Conditions ◽  
Defect Centres

Glasses of the GexS100-x system were studied in the region of 30 ⪬ x ⪬ 45. The concept of magnetically active defect centres was employed to account for the EPR spectra of pure samples as well as those doped with silver or iodine, prepared in different temperature conditions. In terms of this concept a consistent interpretation of the experimental data could be given for the composition region applied.

Combined analysis of chemical bonding in a CuIIdimer using QTAIM, Voronoi tessellation and Hirshfeld surface approaches

2015 ◽  
Vol 71 (5) ◽  
pp. 543-554 ◽  
Author(s):  
Anna V. Vologzhanina ◽  
Svitlana V. Kats ◽  
Larisa V. Penkova ◽  
Vadim A. Pavlenko ◽  
Nikolay N. Efimov ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Density Functional ◽  
Voronoi Tessellation ◽  
Quantitative Description ◽  
Hirshfeld Surface ◽  
Epr Spectra ◽  
Antiferromagnetic Coupling ◽  
X Ray Diffraction ◽  
Spin Distribution ◽  
X Ray

Interaction of 1-(1H-pyrazol-5-yl)ethanone oxime (H2PzOx) with copper(II) chloride in the presence of pyridine afforded a binuclear discrete [Cu2(HPzOx)2Cl2py2] complex, which was characterized by Fourier transform–IR and electron paramagnetic resonance (EPR) spectra, magnetochemistry and high-resolution X-ray diffraction experiments. Multipole refinement of X-ray diffraction data and density-functional theory (DFT) calculations of an isolated molecule allowed charge and spin distributions to be obtained for this compound. Magnetochemistry data, EPR spectra and DFT calculations of an isolated molecule show antiferromagnetic coupling between copper(II) ions. The spin distribution suggests an exchange pathwayviathe bridging pyrazole ring in the equatorial plane of the CuN4Cl coordination polyhedron, thus providing support for the classical superexchange mechanism; the calculated value of the magnetic coupling constant −2Jis equal to 220 cm−1, which compares well with the experimental value of 203 ± 2 cm−1. Chemical connectivity was derived by Bader's `quantum theory of atoms in molecules' and compared with Voronoi tessellation and Hirshfeld surface representations of crystal space. All methodologies gave a similar qualitative and semi-quantitative description of intra- and intermolecular connectivity.

scholarly journals Влияние межатомного обменного взаимодействия на магнитные фазовые переходы в условиях спинового кроссовера при высоких давлениях

2018 ◽  
Vol 60 (6) ◽  
pp. 1166
Author(s):  
С.Г. Овчинников ◽  
Ю.С. Орлов ◽  
С.В. Николаев ◽  
А.И. Нестеров ◽  
Т.М. Овчинникова
Keyword(s):  
Experimental Data ◽  
Phase Diagram ◽  
High Spin ◽  
Spin State ◽  
Pressure Dependence ◽  
Spin Crossover ◽  
External Pressure ◽  
Exchange Integral

AbstractThe phase diagram of an antiferromagnet with the spin crossover from the high-spin to low-spin state with S = 0 with increasing external pressure has been calculated with regard to the pressure dependence of the exchange integral. The calculated results are compared with the experimental data on ferropericlase Fe_ x Mg_1 – x O.

Study of Hydrogen Bonding in Carboxylic Acids by the MNDO/M Method

1994 ◽  
Vol 59 (6) ◽  
pp. 1251-1260 ◽  
Author(s):  
Michal Bureš ◽  
Jaroslav Bezus
Keyword(s):  
Experimental Data ◽  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Carboxylic Acids ◽  
Promising Method ◽  
Semiempirical Methods ◽  
Am1 Method ◽  
Bond Lengths ◽  
Pm3 Method

The semiempirical methods MNDO/M, AM1 and PM3 were applied to the study of hydrogen bonds in carboxylic acids. The calculated hydrogen bond lengths and enthalpies of dimerization were compared with experimental data. The AM1 method fails to properly describe systems with strong hydrogen bonds. The PM3 method predicts the hydrogen bond lengths correctly but underestimates systematically the enthalpies of dimerization. MNDO/M appears to be a promising method for the treatment of association of carboxylic acids.

Synthesis and spectroscopic properties of LiIn(WO4)2 nanopowders and single crystals doped with chromium(III) ions

Open Physics ◽  
2013 ◽  
Vol 11 (11) ◽  
Author(s):  
Tomasz Skibiński ◽  
Hubert Fuks ◽  
Sławomir Kaczmarek ◽  
Tomasz Bodziony ◽  
Krzysztof Hermanowicz ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Single Crystals ◽  
Spectroscopic Data ◽  
High Field ◽  
Spectroscopic Properties ◽  
Epr Spectra ◽  
Higher Spin ◽  
Field Lines ◽  
The Magnetic Field

AbstractLiIn(WO4)2 single crystals and nanopowders doped with chromium(III) ions were synthesized and investigated, including their EPR spectra and magnetic properties. The EPR spectra have shown low and high field lines attributed to isolated chromium ions with an electron spin S=3/2 and complex chromium centers with higher spin value, respectively. Magnetic susceptibility measurements revealed an almost linear dependence on the magnetic field. The electron resonance and magnetic properties have been related to the structural and spectroscopic data of the studied material.

Subchannel Analysis with Mechanistic Methods for Thermo-Hydro Dynamics in BWR Fuel Bundles

2006 ◽  
Author(s):  
Kentaro Imura ◽  
Kenji Yoshida ◽  
Isao Kataoka ◽  
Masanori Naitoh
Keyword(s):  
Experimental Data ◽  
Predictive Accuracy ◽  
Distribution Data ◽  
Two Phase ◽  
Cross Sectional ◽  
Operational Parameter ◽  
Transition Analysis ◽  
Operational Conditions ◽  
Void Distribution ◽  
The Impact

In order to predict the critical power or void fraction in BWR fuel bundles and the DNB heat flux of PWR fuel assemblies, the boiling transition analysis code called “CAPE” with mechanistic models has been developed in the IMPACT project by NUPEC. The objective of the CAPE code development is to perform with good accuracy the safety evaluation for a new type or improved fuel bundle design of BWR and PWR without full-scale experiments or any tuning parameters in the analysis code. In this study, the CAPE for BWR was validated by the test analysis for 8 × 8 fuel bundles comparing with the void distribution data of the experimental data, which was carried out under several operational conditions in a BWR. The computations were carried out by changing the operational parameter such as the inlet subcooling, mass flow rate and the power output of the fuel bundles. Resultantly, the thermal equilibrium quality at the outlet ranges from 2% to 25%. From these results, though the predictive accuracy of the analytical results are in close agreement with the experimental data, it was noted that the errors were relatively outstanding in some subchannels, which was surrounded by the heated fuel rods and partially unheated walls, such as an unheated rod, a water rod and a separation wall of the channel box. The reason for this error is thought to be that the cross sectional void distribution was partially distributed in such subchannels surrounded partially by unheated wall, so the multidimensional void distribution structure might be formed in these subchannels. Under such conditions, it is very important to take into consideration the multidimensional structure of the two-phase flow in subchannel, and perhaps improve the estimation or correlations for the distribution parameter, as well as the amount of void exchange between neighboring subchannels.

scholarly journals VACUUM BIREFRINGENCE CAUSED BY ARBITRARY SPIN PARTICLES

2008 ◽  
Vol 23 (04) ◽  
pp. 245-248 ◽  
Author(s):  
S. I. KRUGLOV
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Laser Beam ◽  
Transverse Magnetic Field ◽  
Vacuum Polarization ◽  
Transverse Magnetic ◽  
Arbitrary Spin ◽  
Effective Lagrangian ◽  
Linearly Polarized ◽  
Higher Spin

We study the propagation of a linearly polarized laser beam in the external transverse magnetic field taking into consideration the vacuum polarization by arbitrary spin particles. Induced ellipticity of the beam is evaluated using the effective Lagrangian. With the help of the PVLAS experimental data, we obtain bounds on masses of charged higher spin particles contributed to ellipticity.

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