scholarly journals Direct light–induced spin transfer between different elements in a spintronic Heusler material via femtosecond laser excitation

2020 ◽  
Vol 6 (3) ◽  
pp. eaaz1100 ◽  
Author(s):  
Phoebe Tengdin ◽  
Christian Gentry ◽  
Adam Blonsky ◽  
Dmitriy Zusin ◽  
Michael Gerrity ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Time Scales ◽  
Density Functional ◽  
Laser Excitation ◽  
High Harmonic ◽  
Density Functional Theory Calculations ◽  
Spin Transfer ◽  
Magnetic Interactions ◽  
Magnetic Sublattice ◽  
Wide Range

Heusler compounds are exciting materials for future spintronics applications because they display a wide range of tunable electronic and magnetic interactions. Here, we use a femtosecond laser to directly transfer spin polarization from one element to another in a half-metallic Heusler material, Co2MnGe. This spin transfer initiates as soon as light is incident on the material, demonstrating spatial transfer of angular momentum between neighboring atomic sites on time scales < 10 fs. Using ultrafast high harmonic pulses to simultaneously and independently probe the magnetic state of two elements during laser excitation, we find that the magnetization of Co is enhanced, while that of Mn rapidly quenches. Density functional theory calculations show that the optical excitation directly transfers spin from one magnetic sublattice to another through preferred spin-polarized excitation pathways. This direct manipulation of spins via light provides a path toward spintronic devices that can operate on few-femtosecond or faster time scales.

Interfacial defect engineering and Photocatalysis Properties of hBN/MX2(M = Mo, W, and X = S, Se) Heterostructures

2021 ◽  
Author(s):  
Zhihai Sun ◽  
Jiaxi Liu ◽  
Ying Zhang ◽  
Ziyuan Li ◽  
Leyu Peng ◽  
...  
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Band Alignment ◽  
Type I ◽  
Defect Engineering ◽  
Wide Range ◽  
Interfacial Defects ◽  
Significant Research ◽  
P Type ◽  
The Impact

Abstract Van der Waals (VDW) heterostructures have attracted significant research interest due to their tunable interfacial properties and potential in a wide range of applications such as electronics, optoelectronic, and heterocatalysis. In this work, the impact of interfacial defects on the electronic structures and photocatalytic properties of hBN/MX2(M = Mo, W, and X = S, Se) are studied using density functional theory calculations. The results reveal that the band alignment of hBN/MX2 can be adjusted by introducing vacancies and atomic doping. The type-I band alignment of the host structure was maintained in the heterostructure with n-type doping in the hBN sublayer. Interestingly, the band alignment changed to the type-II heterostructrue as VB defect and p-type doping was introduced in the hBN sublayer. This could be profitable for the separation of photo-generated electron−hole pairs at the interfaces and is highly desired for heterostructure photocatalysis. In addition, two Z-type heterostructures including hBN(BeB)/MoS2, hBN(BeB)/MoSe2, and hBN(VN)/MoSe2 were achieved, showing reducing band gap and ideal redox potential for water splitting. Our results reveal the possibility of engineering the interfacial and photocatalysis properties of hBN/MX2 heterostructures via interfacial defects.

scholarly journals Selective 13C labelling reveals the electronic structure of flavocoenzyme radicals

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Erik Schleicher ◽  
Stephan Rein ◽  
Boris Illarionov ◽  
Ariane Lehmann ◽  
Tarek Al Said ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Blue Light ◽  
Density Functional ◽  
Double Resonance ◽  
Density Functional Theory Calculations ◽  
Microwave Frequency ◽  
Fine Tuning ◽  
Electron Nuclear Double Resonance ◽  
Intermediate Radical ◽  
Wide Range

AbstractFlavocoenzymes are nearly ubiquitous cofactors that are involved in the catalysis and regulation of a wide range of biological processes including some light-induced ones, such as the photolyase-mediated DNA repair, magnetoreception of migratory birds, and the blue-light driven phototropism in plants. One of the factors that enable versatile flavin-coenzyme biochemistry and biophysics is the fine-tuning of the cofactor’s frontier orbital by interactions with the protein environment. Probing the singly-occupied molecular orbital (SOMO) of the intermediate radical state of flavins is therefore a prerequisite for a thorough understanding of the diverse functions of the flavoprotein family. This may be ultimately achieved by unravelling the hyperfine structure of a flavin by electron paramagnetic resonance. In this contribution we present a rigorous approach to obtaining a hyperfine map of the flavin’s chromophoric 7,8-dimethyl isoalloxazine unit at an as yet unprecedented level of resolution and accuracy. We combine powerful high-microwave-frequency/high-magnetic-field electron–nuclear double resonance (ENDOR) with 13C isotopologue editing as well as spectral simulations and density functional theory calculations to measure and analyse 13C hyperfine couplings of the flavin cofactor in DNA photolyase. Our data will provide the basis for electronic structure considerations for a number of flavin radical intermediates occurring in blue-light photoreceptor proteins.

scholarly journals Star-shaped and linear π-conjugated oligomers consisting of a tetrathienoanthracene core and multiple diketopyrrolopyrrole arms for organic solar cells

2016 ◽  
Vol 12 ◽  
pp. 1459-1466 ◽  
Author(s):  
Hideaki Komiyama ◽  
Chihaya Adachi ◽  
Takuma Yasuda
Keyword(s):  
Solar Cells ◽  
Organic Solar Cells ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Fullerene Derivative ◽  
Conjugated Oligomers ◽  
Visible Absorption ◽  
Photovoltaic Properties ◽  
Wide Range ◽  
Visible Wavelengths

Solution-processable star-shaped and linear π-conjugated oligomers consisting of an electron-donating tetrathienoanthracene (TTA) core and electron-accepting diketopyrrolopyrrole (DPP) arms, namely, TTA-DPP4 and TTA-DPP2, were designed and synthesized. Based on density functional theory calculations, the star-shaped TTA-DPP4 has a larger oscillator strength than the linear TTA-DPP2, and consequently, better photoabsorption property over a wide range of visible wavelengths. The photovoltaic properties of organic solar cells based on TTA-DPP4 and TTA-DPP2 with a fullerene derivative were evaluated by varying the thickness of the bulk heterojunction active layer. As a result of the enhanced visible absorption properties of the star-shaped π-conjugated structure, better photovoltaic performances were obtained with relatively thin active layers (40–60 nm).

scholarly journals Correlation effects in the ground state of Ni-(Co)-Mn-Sn Heusler compounds

MRS Advances ◽  
2019 ◽  
Vol 4 (08) ◽  
pp. 441-446 ◽  
Author(s):  
Bernardo Barbiellini ◽  
Aki Pulkkinen ◽  
Johannes Nokelainen ◽  
Vasiliy Buchelnikov ◽  
Vladimir Sokolovskiy ◽  
...  
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Equilibrium Structure ◽  
Phase Correlation ◽  
Magnetic Interactions ◽  
Magnetic Impurities ◽  
Correlation Effects ◽  
Generalized Gradient ◽  
Co Doping

AbstractWe present density functional theory calculations to study the interplay between magnetic and structural properties in Ni-Co-Mn-Sn. The relative stability of austenite (cubic) and martensite (tetragonal) phases depends critically on the magnetic interactions between Mn atoms. While the standard generalized gradient approximation (GGA) stabilizes the latter phase, correlation effects beyond GGA tend to suppress this effect. Mn atoms treated as magnetic impurities can explain our results, where a delicate balance between magnetic interactions mediated by Ni d and Sn p orbitals determines the equilibrium structure of the crystal. Finally, we discuss the role of Co doping in stabilizing ferromagnetic austenite phases.

scholarly journals New information of dopaminergic agents based on quantum chemistry calculations

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Guillermo Goode-Romero ◽  
Ulrika Winnberg ◽  
Laura Domínguez ◽  
Ilich A. Ibarra ◽  
Rubicelia Vargas ◽  
...  
Keyword(s):  
Density Functional ◽  
Clinical Decision Making ◽  
Chemical Reactivity ◽  
Density Functional Theory Calculations ◽  
Clinical Decision ◽  
Underlying Mechanism ◽  
New Information ◽  
Quantum Chemistry Calculations ◽  
Wide Range ◽  
Donor Acceptor

AbstractDopamine is an important neurotransmitter that plays a key role in a wide range of both locomotive and cognitive functions in humans. Disturbances on the dopaminergic system cause, among others, psychosis, Parkinson’s disease and Huntington’s disease. Antipsychotics are drugs that interact primarily with the dopamine receptors and are thus important for the control of psychosis and related disorders. These drugs function as agonists or antagonists and are classified as such in the literature. However, there is still much to learn about the underlying mechanism of action of these drugs. The goal of this investigation is to analyze the intrinsic chemical reactivity, more specifically, the electron donor–acceptor capacity of 217 molecules used as dopaminergic substances, particularly focusing on drugs used to treat psychosis. We analyzed 86 molecules categorized as agonists and 131 molecules classified as antagonists, applying Density Functional Theory calculations. Results show that most of the agonists are electron donors, as is dopamine, whereas most of the antagonists are electron acceptors. Therefore, a new characterization based on the electron transfer capacity is proposed in this study. This new classification can guide the clinical decision-making process based on the physiopathological knowledge of the dopaminergic diseases.

Stable sodium-sulfur electrochemistry enabled by phosphorus-based complexation

2021 ◽  
Vol 118 (49) ◽  
pp. e2116184118
Author(s):  
Chuanlong Wang ◽  
Yue Zhang ◽  
Yiwen Zhang ◽  
Jianmin Luo ◽  
Xiaofei Hu ◽  
...  
Keyword(s):  
Electrochemical Properties ◽  
Density Functional ◽  
Room Temperature ◽  
Solid Phase ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Wide Range ◽  
Sulfur Battery ◽  
Sodium Sulfur Battery ◽  
Sodium Sulfur

A series of sodium phosphorothioate complexes are shown to have electrochemical properties attractive for sodium-sulfur battery applications across a wide operating temperature range. As cathode materials, they resolve a long-standing issue of cyclic liquid–solid phase transition that causes sluggish reaction kinetics and poor cycling stability in conventional, room-temperature sodium-sulfur batteries. The cathode chemistry yields 80% cyclic retention after 400 cycles at room temperature and a superior low-temperature performance down to −60 °C. Coupled experimental characterization and density functional theory calculations revealed the complex structures and electrochemical reaction mechanisms. The desirable electrochemical properties are attributed to the ability of the complexes to prevent the formation of solid precipitates over a fairly wide range of voltage.

scholarly journals A priori calculations of the free energy of formation from solution of polymorphic self-assembled monolayers

2015 ◽  
Vol 112 (45) ◽  
pp. E6101-E6110 ◽  
Author(s):  
Jeffrey R. Reimers ◽  
Dwi Panduwinata ◽  
Johan Visser ◽  
Yiing Chin ◽  
Chunguang Tang ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
A Priori ◽  
Pyrolytic Graphite ◽  
Density Functional Theory Calculations ◽  
Self Assembled Monolayer ◽  
Atomic Structures ◽  
Wide Range ◽  
Entropy Effects ◽  
Self Assembled

Modern quantum chemical electronic structure methods typically applied to localized chemical bonding are developed to predict atomic structures and free energies for meso-tetraalkylporphyrin self-assembled monolayer (SAM) polymorph formation from organic solution on highly ordered pyrolytic graphite surfaces. Large polymorph-dependent dispersion-induced substrate−molecule interactions (e.g., −100 kcal mol−1 to −150 kcal mol−1 for tetratrisdecylporphyrin) are found to drive SAM formation, opposed nearly completely by large polymorph-dependent dispersion-induced solvent interactions (70–110 kcal mol−1) and entropy effects (25–40 kcal mol−1 at 298 K) favoring dissolution. Dielectric continuum models of the solvent are used, facilitating consideration of many possible SAM polymorphs, along with quantum mechanical/molecular mechanical and dispersion-corrected density functional theory calculations. These predict and interpret newly measured and existing high-resolution scanning tunnelling microscopy images of SAM structure, rationalizing polymorph formation conditions. A wide range of molecular condensed matter properties at room temperature now appear suitable for prediction and analysis using electronic structure calculations.

scholarly journals Structural and Magnetic Studies on Nickel(II) and Cobalt(II) Complexes with Polychlorinated Diphenyl(4-pyridyl)methyl Radical Ligands

Molecules ◽  
2021 ◽  
Vol 26 (18) ◽  
pp. 5596
Author(s):  
Ryota Matsuoka ◽  
Tatsuhiro Yoshimoto ◽  
Yasutaka Kitagawa ◽  
Tetsuro Kusamoto
Keyword(s):  
Metal Ions ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Building Blocks ◽  
Magnetic Interactions ◽  
Organic Radical ◽  
Methyl Radical ◽  
Magnetic Studies ◽  
Orthogonal Relationship ◽  
Magnetic Metal

New magnetic metal complexes with organic radical ligands, [M(hfac)2(PyBTM)2] (M = NiII, CoII; hfac = hexafluoroacetylacetonato, PyBTM = (3,5-dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl radical), were prepared and their crystal structures, magnetic properties, and electronic structures were investigated. Metal ions in [M(hfac)2(PyBTM)2] constructed distorted octahedral coordination geometry, where the two PyBTM molecules ligated in the trans configuration. Magnetic investigation using a SQUID magnetometer revealed that χT increased with decreasing temperature from 300 K in the two complexes, indicating an efficient intramolecular ferromagnetic exchange interaction taking place between the spins on PyBTM and M with J/kB of 21.8 K and 11.8 K for [NiII(hfac)2(PyBTM)2] and [CoII(hfac)2(PyBTM)2]. The intramolecular ferromagnetic couplings in the two complexes could be explained by density functional theory calculations, and would be attributed to a nearly orthogonal relationship between the spin orbitals on PyBTM and the metal ions. These results demonstrate that pyridyl-containing triarylmethyl radicals are key building blocks for magnetic molecular materials with controllable/predictable magnetic interactions.

A Novel µ1,1-Azido-, µ2-Alkoxo-, and µ2-Phenoxo-Bridged Tetranuclear Copper(II) Complex with a Quinquedentate Schiff-Base Ligand: Magneto-Structural and DFT Studies

2009 ◽  
Vol 62 (4) ◽  
pp. 366 ◽  
Author(s):  
Subhra Basak ◽  
Soma Sen ◽  
Georgina Rosair ◽  
Cédric Desplanches ◽  
Eugenio Garribba ◽  
...  
Keyword(s):  
Schiff Base ◽  
Schiff Base Ligand ◽  
Density Functional ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Variable Temperature ◽  
Density Functional Theory Calculations ◽  
Magnetic Interactions ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Ft Ir

A novel tetranuclear copper(ii) complex [Cu4L2(μ1,1- N3)2]·CH3CN (1) has been synthesized using a symmetrical quinquedentate N2O3-donor Schiff-base ligand H3L (N,N′-(2-hydroxypropane-1,3-diyl)bis(2- hydroxyacetophenimine)) and characterized by elemental analysis, Fourier-transform (FT)-IR, UV-visible, electron paramagnetic resonance spectroscopy, and cyclic voltammetry. The X-ray single-crystal structure of 1 reveals three kinds of bridges among the four metal centres: one from the exogenous azido ligand and two from the phenoxo and alkoxo moieties of the Schiff base. The same structure highlights the remarkable versatility of copper(ii) to adopt an array of stereochemistries. Four unusual eight-membered metallacycles exist in 1. The μ1,1-azido, μ2-alkoxo, and μ2-phenoxo bridges among the four copper centres have facilitated interesting magnetic interactions that have been elucidated by variable-temperature magnetic susceptibility measurements and backed up by density functional theory calculations. Detailed analyses have shown that the antiferromagnetic effect through the alkoxo-bridged CuII centres combined with the ferromagnetic interaction through the azido-bridged metal centres results in an S = 0 ground state.

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