scholarly journals Magnetic anisotropy and stability of Fe3Ga compounds

2021 ◽  
Vol 5 (4) ◽  
pp. 229-235
Author(s):  
T. M. Inerbaev ◽  
A. U. Abuova ◽  
A. K. Dauletbekova ◽  
F. U. Abuova ◽  
G. A. Kaptagay ◽  
...  
Keyword(s):  
Magnetic Anisotropy ◽  
Density Functional ◽  
Anisotropy Energy ◽  
Magnetic Anisotropy Energy ◽  
Phonon Spectra ◽  
The Density Functional Theory ◽  
The Difference ◽  
Structure Lead ◽  
The Stability ◽  
Crystal Modifications

The magnetic anisotropy energy and the stability of crystal modifications of D03 and L21 of Fe3Ga compounds are studied with the density functional theory methods. The magnetic anisotropy energy of the D03 structure is more than twice the same value for the L21 structure. The features in the electronic structure lead to the difference in the magnitude of spin-orbit interaction, explaining the found effect. The L21 structure is more thermodynamically stable in the entire range of the considered pressures. Under pressure, the considered crystal modifications of Fe3Ga lose their stability due to the appearance of imaginary frequencies in their phonon spectra.

scholarly journals The difference in stability between 5′R and 5′S diastereomers of 5′,8-cyclopurine-2′-deoxynucleosides. DFT study in gaseous and aqueous phase

2010 ◽  
Vol 8 (1) ◽  
pp. 134-141 ◽  
Author(s):  
Boleslaw Karwowski
Keyword(s):  
Density Functional ◽  
Bond Cleavage ◽  
Basis Set ◽  
Small Range ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Formic Acid Hydrolysis ◽  
The Difference ◽  
The Stability ◽  
First Time

AbstractOxidatively generated damage to DNA frequently appears in the human genome as an effect of aerobic metabolism or as the result of exposure to exogenous oxidizing agents. Due to these facts it has been decided to calculate the stability of 5′,8-cyclo-2′-deoxyadenosine/guanosine (cdA, cdG) in their 5′R and 5′S diastereomeric forms. For all points of quantum mechanics studies presented, the density functional theory (DFT) with B3LYP parameters on 6-311++G** basis set level was used. The calculations showed a significant negative enthalpy for glycosidic bond cleavage reaction for cationic forms and slightly negative for neutral ones. The preliminary study of the discussed process has shown the nature of stepwise nucleophilic substitution DN*AD type mechanism. Surprisingly, the different values in free energy, between short-lived oxacarbenium ion intermediates, have been found to lie over a relatively small range, around 1 and 2.8 kcal mol−1. For anions, the decomposition enthalpies were found as positive in aqueous phases. These theoretical results are supported by the formic acid hydrolysis experiments of both diastereomers of cdA, for the first time. (5′S)cdA exhibited higher stability than (5′R)cdA.

scholarly journals Magnetic properties of free-standing finite linear Co chains

2018 ◽  
Vol 64 (5) ◽  
pp. 483 ◽  
Author(s):  
Julio Cesar Hernandez-Herrejon ◽  
Rodrigo Chavez-Alcazar
Keyword(s):  
Magnetic Properties ◽  
Magnetic Anisotropy ◽  
Density Functional ◽  
Finite Size ◽  
Anisotropy Energy ◽  
Spin Moment ◽  
Generalized Gradient ◽  
Free Standing ◽  
Magnetic Anisotropy Energy ◽  
Atomic Chains

The ground state magnetic properties of Co_N linear atomic chains with 1 ≤ N ≤ 10 are studied within density functional theory using the generalized gradient approximation . A linear scaling between the binding energy per atom and the inverse of the number of atoms in the chain is found. For the optimized geometries, our results show a dimerization effect for chains of few atoms but for bigger ones the phenomena disappear in the center but remains at the ends due to finite size effects. The spin moment, the orbital moment and the magnetic anisotropy energy were investigated. For large chains, the orbital and spin moments have a tendency to become uniform. Enhanced spin and orbital moments were found due to the reduced coordination number compared to the cobalt in bulk. The cobalt chain of five atoms has the biggest magnetic anisotropy energy with an outstanding 8 meV, suggesting that it could have applications in ultrahigh density magnetic memories and hard disk. 

scholarly journals Anatomy of Magnetic Anisotropy and Voltage-Controlled Magnetic Anisotropy in Metal Oxide Heterostructure from First Principles

Crystals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1118
Author(s):  
Indra Pardede ◽  
Daiki Yoshikawa ◽  
Tomosato Kanagawa ◽  
Nurul Ikhsan ◽  
Masao Obata ◽  
...  
Keyword(s):  
Magnetic Anisotropy ◽  
Density Functional ◽  
Compressive Strain ◽  
Magnetic Tunnel Junction ◽  
Dipole Interaction ◽  
Anisotropy Energy ◽  
Strain Effect ◽  
Spin Orbit ◽  
Magnetic Anisotropy Energy ◽  
Oxide Heterostructure

Voltage control of magnetic anisotropy (VCMA) is one of the promising approaches for magnetoelectric control of magnetic tunnel junction (MTJ). Here, we systematically calculated the magnetic anisotropy (MA) and the VCMA energies in the well-known MTJ structure consisting of Fe/MgO interface with Cr buffer layer. In this calculation, we investigated an alloying between Fe and Cr and a strain effect. We used a spin density functional approach which includes both contributions from magnetocrystalline anisotropy energy (MCAE) originating from spin–orbit coupling and shape magnetic anisotropy energy from spin dipole–dipole interaction. In the present approach, the MCAE part, in addition to a common scheme of total energy, was evaluated using a grand canonical force theorem scheme. In the latter scheme, atom-resolved and k-resolved analyses for MA and VCMA can be performed. At first, we found that, as the alloying is introduced, the perpendicular MCAE increases by a factor of two. Next, as the strain is introduced, we found that the MCAE increases with increasing compressive strain with the maximum value of 2.2 mJ/m2. For the VCMA coefficient, as the compressive strain increases, the sign becomes negative and the absolute value becomes enhanced to the number of 170 fJ/Vm. By using the atom-resolved and k-resolved analyses, we clarified that these enhancements of MCAE and VCMA mainly originates from the Fe interface with MgO (Fe1) and are located at certain lines in the two dimensional Brillouin zone. The findings on MCAE and VCMA are fully explained by the spin-orbit couplings between the certain d-orbital states in the second-order perturbation theory.

scholarly journals Ultrafast femtosecond pressure modulation of structure and exciton kinetics in 2D halide perovskites for enhanced light response and stability

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chunpeng Song ◽  
Huanrui Yang ◽  
Feng Liu ◽  
Gary J. Cheng
Keyword(s):  
Femtosecond Laser ◽  
Density Functional ◽  
Thermal Conditions ◽  
Light Response ◽  
Shock Pressure ◽  
Laser Shock Processing ◽  
The Density Functional Theory ◽  
Pressure Modulation ◽  
The Stability ◽  
Inorganic Framework

AbstractThe carriers’ transportation between layers of two-dimensional (2D) perovskites is inhibited by dielectric confinement. Here, for the first time, we employ a femtosecond laser to introduce ultrafast shock pressure in the range of 0~15.45 GPa to reduce dielectric confinement by modulating the structure and exciton dynamics in a perovskite single crystal (PSCs), e.g. (F-PEA)2PbI4 (4-fluorophenethylammonium, F-PEA). The density functional theory (DFT) simulation and experimental results show that the inorganic framework distortion results in a bandgap reduction. It was found that the exciton-optical phonon coupling and free excitons (FEs) binding energy are minimized at 2.75 GPa shock pressure due to a reduction in dielectric confinement. The stability testing under various harsh light and humid thermal conditions shows that femtosecond laser shocking improves the stability of (F-PEA)2PbI4 PSCs. Femtosecond laser shock processing provides a new approach for regulating the structure and enhancing halide perovskite properties.

Magnetic anisotropy energy of antiferromagnetic coupled Fe/Cr/Fe layers (abstract)

1991 ◽  
Vol 69 (8) ◽  
pp. 5321-5321
Author(s):  
C. M. Williams ◽  
J. J. Krebs ◽  
G. A. Prinz ◽  
A. Chaiken
Keyword(s):  
Magnetic Anisotropy ◽  
Anisotropy Energy ◽  
Magnetic Anisotropy Energy

Study of the Stability and Chemical Reactivity of a Series of Tetrazole Pyrimidine Hybrids by the Density Functional Theory Method (DFT)

2021 ◽  
Vol 37 (4) ◽  
pp. 805-812
Author(s):  
Ahissandonatien Ehouman ◽  
Adjoumanirodrigue Kouakou ◽  
Fatogoma Diarrassouba ◽  
Hakim Abdel Aziz Ouattara ◽  
Paulin Marius Niamien
Keyword(s):  
Density Functional ◽  
Theoretical Study ◽  
Molecular Descriptors ◽  
Chemical Reactivity ◽  
Density Functional Theory Method ◽  
Functional Theory ◽  
Reactivity Descriptors ◽  
The Density Functional Theory ◽  
The Stability ◽  
Global Reactivity Descriptors

Our theoretical study of stability and reactivity was carried out on six (06) molecules of a series of pyrimidine tetrazole hybrids (PTH) substituted with H, F, Cl, Br, OCH3 and CH3 atoms and groups of atoms using the density function theory (DFT). Analysis of the thermodynamic formation quantities confirmed the formation and existence of the series of molecules studied. Quantum chemical calculations at the B3LYP / 6-311G (d, p) level of theory determined molecular descriptors. Global reactivity descriptors were also determined and analyzed. Thus, the results showed that the compound PTH_1 is the most stable, and PTH_5 is the most reactive and nucleophilic. Similarly, the compound PTH_4 is the most electrophilic. The analysis of the local descriptors and the boundary molecular orbitals allowed us to identify the preferred atoms for electrophilic and nucleophilic attacks.

Comparison between Magnetic Anisotropy Energy and a Parameter to the Assessment of Magnetic Property of Electrical Steel

2018 ◽  
Vol 930 ◽  
pp. 449-453
Author(s):  
R.A.C. Felix ◽  
R.L.O. da Rosa ◽  
Luiz P. Brandão
Keyword(s):  
Magnetic Properties ◽  
Magnetic Property ◽  
Magnetic Anisotropy ◽  
Electrical Steel ◽  
Anisotropy Energy ◽  
Alternative Methods ◽  
Magnetic Polarization ◽  
Magnetic Anisotropy Energy ◽  
Electrical Steels ◽  
Global Parameters

Alternative methods of quantitative texture analysis are applied to characterize the non-oriented grain electrical steels (NOG) in relation to their magnetic properties. Magnetic anisotropy energy (Ea) and A parameter are two models based on crystallographic texture that generates global parameters that can be used to predict the magnetic properties of NOG steels. In this work, these two models were used to evaluate the magnetic polarization and compared between themselves to realize which one best correlates to this property.

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