scholarly journals Anisotropic Landau-Lifshitz model in discrete space-time

2021 ◽  
Vol 11 (3) ◽  
Author(s):  
Žiga Krajnik ◽  
Enej Ilievski ◽  
Tomaz Prosen ◽  
Vincent Pasquier
Keyword(s):  
Easy Axis ◽  
Chemical Potential ◽  
Diffusion Constant ◽  
Uniaxial Anisotropy ◽  
Space Time ◽  
Discrete Space ◽  
Integration Scheme ◽  
Integrable Lattice ◽  
Drude Weight ◽  
And Diffusion

We construct an integrable lattice model of classical interacting spins in discrete space-time, representing a discrete-time analogue of the lattice Landau-Lifshitz ferromagnet with uniaxial anisotropy. As an application we use this explicit discrete symplectic integration scheme to compute the spin Drude weight and diffusion constant as functions of anisotropy and chemical potential. We demonstrate qualitatively different behavior in the easy-axis and the easy-plane regimes in the non-magnetized sector. Upon approaching the isotropic point we also find an algebraic divergence of the diffusion constant, signaling a crossover to spin superdiffusion.

scholarly journals Water and Deuterium Oxide Permeability through Aquaporin 1: MD Predictions and Experimental Verification

2007 ◽  
Vol 130 (1) ◽  
pp. 111-116 ◽  
Author(s):  
Artem B. Mamonov ◽  
Rob D. Coalson ◽  
Mark L. Zeidel ◽  
John C. Mathai
Keyword(s):  
Deuterium Oxide ◽  
Diffusion Constant ◽  
Structural Data ◽  
Md Simulations ◽  
Water Model ◽  
Aquaporin 1 ◽  
Self Diffusion ◽  
Osmotic Permeability ◽  
Protein Channels ◽  
And Diffusion

Determining the mechanisms of flux through protein channels requires a combination of structural data, permeability measurement, and molecular dynamics (MD) simulations. To further clarify the mechanism of flux through aquaporin 1 (AQP1), osmotic pf (cm3/s/pore) and diffusion pd (cm3/s/pore) permeability coefficients per pore of H2O and D2O in AQP1 were calculated using MD simulations. We then compared the simulation results with experimental measurements of the osmotic AQP1 permeabilities of H2O and D2O. In this manner we evaluated the ability of MD simulations to predict actual flux results. For the MD simulations, the force field parameters of the D2O model were reparameterized from the TIP3P water model to reproduce the experimentally observed difference in the bulk self diffusion constants of H2O vs. D2O. Two MD systems (one for each solvent) were constructed, each containing explicit palmitoyl-oleoyl-phosphatidyl-ethanolamine (POPE) phospholipid molecules, solvent, and AQP1. It was found that the calculated value of pf for D2O is ∼15% smaller than for H2O. Bovine AQP1 was reconstituted into palmitoyl-oleoyl-phosphatidylcholine (POPC) liposomes, and it was found that the measured macroscopic osmotic permeability coefficient Pf (cm/s) of D2O is ∼21% lower than for H2O. The combined computational and experimental results suggest that deuterium oxide permeability through AQP1 is similar to that of water. The slightly lower observed osmotic permeability of D2O compared to H2O in AQP1 is most likely due to the lower self diffusion constant of D2O.

scholarly journals Interface Behavior of Brazing between Zr-Cu Filler Metal and SiC Ceramic

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 727
Author(s):  
Bofang Zhou ◽  
Taohua Li ◽  
Hongxia Zhang ◽  
Junliang Hou
Keyword(s):  
Interfacial Reaction ◽  
Reaction Layer ◽  
Chemical Potential ◽  
Filler Metal ◽  
Diffusion Constant ◽  
Interface Reaction ◽  
Diffusion Path ◽  
Interface Behavior ◽  
Interfacial Reaction Layer ◽  
Sic Ceramic

The interface behavior of brazing between Zr-Cu filler metal and SiC ceramic was investigated. Based on the brazing experiment, the formation of brazing interface products was analyzed using OM, SEM, XRD and other methods. The stable chemical potential phase diagram was established to analyze the possible diffusion path of interface elements, and then the growth behavior of the interface reaction layer was studied by establishing relevant models. The results show that the interface reaction between the active element Zr and SiC ceramic is the main reason in the brazing process the interface products are mainly ZrC and Zr2Si and the possible diffusion path of elements in the product formation process is explained. The kinetic equation of interfacial reaction layer growth is established, and the diffusion constant (2.1479 μm·s1/2) and activation energy (42.65 kJ·mol−1) are obtained. The growth kinetics equation of interfacial reaction layer thickness with holding time at different brazing temperatures is obtained.

Diffusion Constant and Diffusion Coefficient

Science ◽  
1955 ◽  
Vol 121 (3137) ◽  
pp. 215-216 ◽  
Author(s):  
J. VERDUIN
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Constant ◽  
And Diffusion

Noncommutative scalar field in de Sitter space–time and pair creation process

2021 ◽  
Vol 36 (02) ◽  
pp. 2150011
Author(s):  
Nabil Mehdaoui ◽  
Lamine Khodja ◽  
Salah Haouat
Keyword(s):  
Scalar Field ◽  
Chemical Potential ◽  
De Sitter Space ◽  
Space Time ◽  
Pair Creation ◽  
De Sitter ◽  
Creation Process ◽  
Scalar Particles ◽  
Constant Electromagnetic Field

In this work, we address the process of pair creation of scalar particles in [Formula: see text] de Sitter space–time in presence of a constant electromagnetic field by applying the noncommutativity on the scalar field up to first-order in [Formula: see text]. We calculate the density of particles created in the vacuum by the mean of the Bogoliubov transformations. In contrast to a previous result, we show that noncommutativity contributes to the pair creation process. We find that the noncommutativity plays the same role of chemical potential and gives an important interest for studies at high energies.

scholarly journals Lower Bounding Diffusion Constant by the Curvature of Drude Weight

2017 ◽  
Vol 119 (8) ◽  
Author(s):  
Marko Medenjak ◽  
Christoph Karrasch ◽  
Tomaž Prosen
Keyword(s):  
Diffusion Constant ◽  
Lower Bounding ◽  
Drude Weight

scholarly journals Dynamics of Magnetization in Multilayer TbCo / FeCo Structures under the Influence of Femtosecond Optical Excitation

2019 ◽  
Vol 7 (3) ◽  
pp. 50-58 ◽  
Author(s):  
N. A. Ilyin ◽  
A. A. Klimov ◽  
N. Tiercelin ◽  
P. Pernod ◽  
E. D. Mishina ◽  
...  
Keyword(s):  
Easy Axis ◽  
Uniaxial Anisotropy ◽  
Anisotropy Field ◽  
Optical Excitation ◽  
Spin Precession ◽  
Heat Diffusion ◽  
Easy Magnetization ◽  
Test Beam ◽  
Magnetic Subsystem ◽  
Hard Axis

The need to study ultrafast processes in magnetism is due to the prospects for creating ultrafast magnetic recording and ultrafast spintronic devices. In order to excite the magnetic subsystem femtosecond optical pulses are used. The excitement is manifested as in spin precession. In metals, the material is heated first due to significant optical absorption, and significant Joule losses occur. The most important task is to search for materials in which spin processes are excited without heating. Obvious candidates are weakly absorbing materials, such as ferrite garnets. However, the range of such materials and the range of their functionality are limited.The purpose of this work is to study the dynamics of systems with nonthermal mechanisms of spin precession excitation. Such excitation is possible in ferromagnetic / antiferromagnetic heterostructures with exchange interaction, provided that the recombination time of photocarriers is shorter than the time of heat diffusion. Multilayer TbCo / FeCo structures of the near IR range were investigated for a femtosecond optical pulse. The spin dynamics are compared with the direction of the wave vector of the exciting pulse along and perpendicular to the axis of easy magnetization of the structures (“easy axis” and “hard axis” geometry, respectively). It is shown that in case of “easy axis” geometry the determinative mechanism is the thermal interaction. When the system is exposed to an excitation pulse, this mechanism leads to a decrease in the projection of magnetization on the direction of propagation of the test beam. In case of “hard axis” geometry, the magnetization turns to the magnetic field at the initial stage. Then it precesses and relaxes to an equilibrium angular orientation. Such dynamics indicate a rapid recovery of the uniaxial anisotropy field after laser irradiation. The presented results demonstrate an ultrafast change in the magnetic anisotropy induced during the fabrication of the heterostructure under study, which may be of interest for optical control of the orientation of the magnetization.

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