scholarly journals Magnetic moment quenching in small Pd clusters in solution

2021 ◽  
Vol 75 (12) ◽  
Author(s):  
Sebastian Hammon ◽  
Linn Leppert ◽  
Stephan Kümmel
Keyword(s):  
Magnetic Moment ◽  
Density Functional ◽  
Magnetic Moments ◽  
Direct Consequence ◽  
Solvation Shell ◽  
Electronic Interaction ◽  
Cluster Geometry ◽  
Pd Clusters ◽  
Solvent Molecules ◽  
Dynamics Simulations

Abstract Small palladium clusters in vacuum show pronounced magnetic moments. With the help of Born–Oppenheimer molecular dynamics simulations based on density functional theory, we investigate for the paradigmatic examples of the Pd$$_{13}$$ 13 and the Pd$$_8$$ 8 cluster whether these magnetic moments prevail when the clusters are solvated. Our results show that the interaction with acetophenone quenches the magnetic moment. The reduction of the magnetic moment is a direct consequence of the electronic interaction between the Pd clusters and the solvent molecules, and not an indirect effect due to a different cluster geometry being stabilized by the solvation shell. Graphical Abstract

ENHANCEMENT OF Fe MAGNETIC MOMENTS IN FERROMAGNETIC Fe16B2, Fe16C2, AND Fe16N2

1993 ◽  
Vol 07 (01n03) ◽  
pp. 729-732 ◽  
Author(s):  
B.I. MIN
Keyword(s):  
Magnetic Moment ◽  
Density Functional ◽  
Local Density ◽  
Magnetic Moments ◽  
Local Environment ◽  
Electronic Structure Calculations ◽  
Orbital Contribution ◽  
Large Enhancement ◽  
Band Method ◽  
Structure Calculations

In order to investigate electronic and magnetic properties of Fe16X2 (X=B, C, N) ferromagnet, we have performed electronic structure calculations employing the total energy self-consistent local density functional linearized muffin tin orbital (LMTO) band method. Large enhancement of the magnetic moment is observed in FeII and FeIII, which are located farther from X than FeI. This suggests that the local environment plays a very important role in determining Fe magnetic moments in these compounds. Orbital contribution to the magnetic moment in Fe atoms of Fe16N2 is minor, totalof ~0.6 μB in the unit cell. We have obtained the average magnetic moments per Fe atom, 2.30, 2.40, and 2.50 μB, in Fe16B2, Fe16C2, and Fe16N2, respectively.

scholarly journals Tuning the Magnetic Moment of Small Late 3d-Transition-Metal Oxide Clusters by Selectively Mixing the Transition-Metal Constituents

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1814
Author(s):  
Rodrigo H. Aguilera-del-Toro ◽  
María B. Torres ◽  
Faustino Aguilera-Granja ◽  
Andrés Vega
Keyword(s):  
Transition Metal ◽  
Metal Oxide ◽  
Magnetic Moment ◽  
Density Functional ◽  
Magnetic Moments ◽  
Metal Oxide Nanoparticles ◽  
Transition Metal Oxide ◽  
Blocking Temperature ◽  
Oxide Nanoparticles ◽  
Oxidation Rates

Transition-metal oxide nanoparticles are relevant for many applications in different areas where their superparamagnetic behavior and low blocking temperature are required. However, they have low magnetic moments, which does not favor their being turned into active actuators. Here, we report a systematical study, within the framework of the density functional theory, of the possibility of promoting a high-spin state in small late-transition-metal oxide nanoparticles through alloying. We investigated all possible nanoalloys An−xBxOm (A, B = Fe, Co, Ni; n = 2, 3, 4; 0≤x≤n) with different oxidation rates, m, up to saturation. We found that the higher the concentration of Fe, the higher the absolute stability of the oxidized nanoalloy, while the higher the Ni content, the less prone to oxidation. We demonstrate that combining the stronger tendency of Co and Ni toward parallel couplings with the larger spin polarization of Fe is particularly beneficial for certain nanoalloys in order to achieve a high total magnetic moment, and its robustness against oxidation. In particular, at high oxidation rates we found that certain FeCo oxidized nanoalloys outperform both their pure counterparts, and that alloying even promotes the reentrance of magnetism in certain cases at a critical oxygen rate, close to saturation, at which the pure oxidized counterparts exhibit quenched magnetic moments.

scholarly journals Hydration interactions beyond the first solvation shell in aqueous phenolate solution

2020 ◽  
Vol 22 (35) ◽  
pp. 19940-19947
Author(s):  
Roberto Cota ◽  
Ambuj Tiwari ◽  
Bernd Ensing ◽  
Huib J. Bakker ◽  
Sander Woutersen
Keyword(s):  
Molecular Dynamics ◽  
Density Functional Theory ◽  
Molecular Dynamics Simulations ◽  
Vibrational Spectroscopy ◽  
Density Functional ◽  
Solvation Shell ◽  
Water Molecules ◽  
Functional Theory ◽  
Ultrafast Vibrational Spectroscopy ◽  
Dynamics Simulations

We investigate the orientational dynamics of water molecules solvating phenolate ions using ultrafast vibrational spectroscopy and density functional theory-based molecular dynamics simulations.

Influence of Co and Mn substitution on magnetic properties of novel Y2FeSi Heusler alloy

2021 ◽  
Vol 35 (05) ◽  
pp. 2150088
Author(s):  
G. Kasprzak ◽  
J. Rzacki
Keyword(s):  
Magnetic Properties ◽  
Spin Polarization ◽  
Magnetic Moment ◽  
Density Functional ◽  
Magnetic Moments ◽  
Heusler Alloys ◽  
Total Magnetic Moment ◽  
Functional Theory ◽  
Structure Changes ◽  
Mn Substitution

This paper presents results of density functional theory (DFT) studies on structural, electronic, and magnetic properties of novel Y2FeSi Heusler material characterized by spin polarization at Fermi level of [Formula: see text] and magnetic moment of 1.56 [Formula: see text]. The total magnetic moment of investigated material is dominated by Iron sites, while magnetic moments coming from Yttrium sites are aligned antiparallel to the Iron. Here, we introduced Co and Mn substitutions to alter the magnetic and electronic properties of the studied material. The Heusler alloys are very sensitive to electronic structure changes induced by ionic substitutions, which allowing to specifically modulate their properties. The Co-substitution lowered the total magnetic moment to [Formula: see text][Formula: see text]1.20 [Formula: see text] and Mn caused a rise to [Formula: see text][Formula: see text]1.93 [Formula: see text]. Introduction of Mn resulted in [Formula: see text] spin polarization. We hope that this study will promote further theoretical as well as experimental interest in these types of compounds.

scholarly journals Do Better Quality Embedding Potentials Accelerate the Convergence of QM/MM Models? The Case of Solvated Acid Clusters

Molecules ◽  
2018 ◽  
Vol 23 (10) ◽  
pp. 2466 ◽  
Author(s):  
Junming Ho ◽  
Yihan Shao ◽  
Jin Kato
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Water Model ◽  
Reaction Centre ◽  
Empirical Methods ◽  
Functional Theory ◽  
Highly Sensitive ◽  
Solvent Molecules ◽  
Dynamics Simulations ◽  
Semi Empirical

This study examines whether the use of more accurate embedding potentials improves the convergence of quantum mechanics/molecular mechanics (QM/MM) models with respect to the size of the QM region. In conjunction with density functional theory calculations using the ωB97X-D functional, various embedding potentials including the TIP3P water model, the effective fragment potential (EFP), and semi-empirical methods (PM6, PM7, and DFTB) were used to simulate the deprotonation energies of solvated acid clusters. The calculations were performed on solvated neutral (HA) and cationic (HB+) acids clusters containing 160 and 480 water molecules using configurations sampled from molecular dynamics simulations. Consistently, the ωB97X-D/EFP model performed the best when using a minimal QM region size. The performance for the other potentials appears to be highly sensitive to the charge character of the acid/base pair. Neutral acids display the expected trend that semi-empirical methods generally perform better than TIP3P; however, an opposite trend was observed for the cationic acids. Additionally, electronic embedding provided an improvement over mechanical embedding for the cationic systems, but not the neutral acids. For the best performing ωB97X-D/EFP model, a QM region containing about 6% of the total number of solvent molecules is needed to approach within 10 kJ mol−1 of the pure QM result if the QM region was chosen based on the distance from the reaction centre.

Theoretical Studies on the Magnetic Moments of Iron Nitrides Including Fe16N2

1993 ◽  
Vol 313 ◽  
Author(s):  
Akimasa Sakuma ◽  
Yutaka Sugita
Keyword(s):  
Magnetic Moment ◽  
Density Functional ◽  
Magnetic Moments ◽  
Iron Nitrides ◽  
Functional Formalism ◽  
Orbital Magnetic Moment ◽  
Spin Polarized ◽  
Calculated Magnetic Moment ◽  
The Difference

ABSTRACTThe spin-polarized band calculations for the iron nitrides, Fe3N, Fe4N and Fe16N2, have been performed with use of LMTO-ASA Method in the frame of local spin density functional formalism. The results show that the most distant Fe atoms from N have the largest magnetic moment. The central role of the N atom is to bring about the large magnetic moments through the lattice expansion. Concurrently, the N atoms promote an itinerancy of electrons and then in turn prevent the exchange-splitting. This results in an Fe16N2 with the lowest N concentration having the largest magnetic moments. Quantitatively, the obtained magnetic moments are in fair agreements with the experimental results except for Fe16Nr The calculated magnetic moment of Fe6N2 is about 2.4 ΜB/Pε, while the measured value is reported as 3.5 ΜB/FB. The orbital magnetic moment of Fe16N2 is about 0.07 ΜB, which is too small to make up for the difference from the experimental value.

Surface-Charge Dependent Orientation of Water at the Interface of a Gold Electrode: A Cluster Study

2018 ◽  
Vol 232 (9-11) ◽  
pp. 1583-1592 ◽  
Author(s):  
Gianluca Fazio ◽  
Gotthard Seifert ◽  
Mathias Rapacioli ◽  
Nathalie Tarrat ◽  
Jan-Ole Joswig
Keyword(s):  
Cluster Model ◽  
Gold Electrode ◽  
Density Functional ◽  
Gold Cluster ◽  
Tight Binding ◽  
Periodic Boundary Conditions ◽  
Solvation Shell ◽  
Screening Behavior ◽  
Self Consistent ◽  
Dynamics Simulations

Abstract A gold/water interface has been investigated with the DFT-based self-consistent-charge density-functional tight-binding (SCC-DFTB) method using a cluster model. Born–Oppenheimer molecular-dynamics simulations for mono-, bi-, and trilayers of water on the surface of a Au55 cluster have been computed. We have demonstrated the applicability of this method to the study of the structural and dynamical properties of the gold/water-multilayer interface. The results of the simulations clearly show the charge-dependent orientation and the corresponding polarization of the water sphere around the gold cluster. However, it was also shown that this polarization is restricted almost only to the first solvation shell. This illustrates the rather short-range screening behavior of water. The present study builds the basis for further investigations of metal/electrolyte interfaces on a reliable atomistic level, avoiding the problems of spurious artifacts in models using periodic boundary conditions.

scholarly journals Element-specific contributions to improved magnetic heating of theranostic CoFe2O4 nanoparticles decorated with Pd

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
S. Fatemeh Shams ◽  
Detlef Schmitz ◽  
Alevtina Smekhova ◽  
Mohammad Reza Ghazanfari ◽  
Margret Giesen ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Density Functional ◽  
Magnetic Circular Dichroism ◽  
Magnetic Moments ◽  
Remarkable Change ◽  
Spin Canting ◽  
Low Field ◽  
Magnetic Heating ◽  
Pd Clusters ◽  
X Ray Absorption

AbstractDecoration with Pd clusters increases the magnetic heating ability of cobalt ferrite (CFO) nanoparticles by a factor of two. The origin of this previous finding is unraveled by element-specific X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD) combined with atomic multiplet simulations and density functional theory (DFT) calculations. While the comparison of XAS spectra with atomic multiplet simulations show that the inversion degree is not affected by Pd decoration and, thus, can be excluded as a reason for the improved heating performance, XMCD reveals two interrelated responsible sources: significantly larger Fe and Co magnetic moments verify an increased total magnetization which enhances the magnetic heating ability. This is accompanied by a remarkable change in the field-dependent magnetization particularly for Co ions which exhibit an increased low-field susceptibility and a reduced spin canting behavior in higher magnetic fields. Using DFT calculations, these findings are explained by reduced superexchange between ions on octahedral lattice sites via oxygen in close vicinity of Pd, which reinforces the dominating antiparallel superexchange interaction between ions on octahedral and tetrahedral lattice sites and thus reduces spin canting. The influence of the delocalized nature of Pd 4d electrons on the neighboring ions is discussed and the conclusions are illustrated with spin density isosurfaces of the involved ions. The presented results pave the way to design nanohybrids with tailored electronic structure and magnetic properties.

THE FIRST PRINCIPLES CALCULATION OF STRUCTURAL, ELECTRONIC AND MAGNETIC PROPERTIES OF MnXY (X = Ru, Rh AND Y = Ga, Ge, Sb) ALLOYS

2011 ◽  
Vol 25 (26) ◽  
pp. 2079-2090 ◽  
Author(s):  
S. M. MONIRI ◽  
Z. NOURBAKHSH ◽  
M. MOSTAJABODAAVATI
Keyword(s):  
Magnetic Properties ◽  
Magnetic Moment ◽  
Density Functional ◽  
Magnetic Moments ◽  
Heusler Alloys ◽  
Local Magnetic Moment ◽  
First Principles Calculation ◽  
Functional Theory ◽  
Half Metallic ◽  
Electronic And Magnetic Properties

The structural, electronic and magnetic properties of MnXY ( X = Ru , Rh and Y = Ga , Ge , Sb ) Heusler alloys are studied using density functional theory by the WIEN2k package. These materials are ferromagnetic. Also they have some interesting half-metallic properties. The electron density of states, total and local magnetic moment of these alloys are calculated. We have calculated the effective Coulomb interaction U eff using the ab initio method. We have compared the magnetic moments of these alloys in GGA and LDA + U with the Slater–Pauling rule. Furthermore the effect of hydrostatic pressure on the magnetic moment of these alloys is studied. The calculated results are fitted with a second order polynomial.

First-Principle Calculations for Magnetism of Mn-Doped Graphene

2013 ◽  
Vol 709 ◽  
pp. 184-187 ◽  
Author(s):  
Jia Jia Liu ◽  
Tian Min Lei ◽  
Yu Ming Zhang ◽  
Pei Ting Ma ◽  
Zhi Yong Zhang
Keyword(s):  
Density Of States ◽  
Magnetic Moment ◽  
Density Functional ◽  
Magnetic Semiconductors ◽  
Magnetic Moments ◽  
Dilute Magnetic Semiconductors ◽  
First Principle ◽  
First Principle Calculation ◽  
Doped Graphene ◽  
Mn Doped

Mn doped graphene-based dilute magnetic semiconductors (DMS) are investigated using the first-principle calculation based on density functional theory. In this paper, the Mn-C bond length, formation energy and magnetic moment are calculated in different doping systems and their density of states is made a detailed analysis. It is found that Mn-doped graphene has strong ferromagnetic properties and the magnetic moments of graphene supercells are different with the impurity concentrations. These supercells of a Mn atom substituting a C atom are increasingly stable with extending cells and the 11×11 supercell possesses the biggest magnetic moment of 3.8μB in these systems. The analysis of the density of states indicates the magnetic properties of Mn-doped graphene derive from the p-d exchange mechanism.

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