scholarly journals Monte Carlo studies on shape deformation and stability of 3D skyrmions under mechanical stresses

2021 ◽  
Vol 2090 (1) ◽  
pp. 012080
Author(s):  
H. Koibuchi ◽  
S. Hongo ◽  
F. Kato ◽  
S. El Hog ◽  
G. Diguet ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Monte Carlo ◽  
Finsler Geometry ◽  
Experimental Studies ◽  
Mechanical Stresses ◽  
Magnetic Field Direction ◽  
Monte Carlo Studies ◽  
Magnetic Orders ◽  
The Stability ◽  
Uniaxial Compressive Stress

Abstract We study the stability/instability of skyrmions under mechanical stresses by Monte Carlo simulations in a 3D disk composed of tetrahedrons. Skyrmions emerge in chiral magnetic materials, such as FeGe and MnSi, under the competition of ferromagnetic interaction (FMI) and Dzyaloshinskii-Moriya interaction (DMI) and are stabilized by the external magnetic field. Recent experimental studies show that skyrmions are also stabilized/destabilized by uniaxial compressive stress perpendicular to or along the magnetic field direction. These phenomena are studied by using a 3D Finsler geometry (FG) model. In this 3D FG model, the DMI coefficient is automatically anisotropic by a geometrically implemented coupling of strains and electronic spins. We find that skyrmions are stabilized (destabilized) by extension (compression) stress along the direction of the applied magnetic field consistent with reported experimental data. This consistency implies that the 3D FG model successfully implements the magnetostrictive or magneto-elastic effect of external mechanical stresses on chiral magnetic orders, including the skyrmion configuration.

Surface levels of organic conductors in a tilted in-plane magnetic field

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Danica Krstovska ◽  
Aleksandar Skeparovski
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Fermi Surface ◽  
Tilt Angle ◽  
Experimental Studies ◽  
Surface States ◽  
Organic Conductors ◽  
Magnetic Field Direction ◽  
Two Dimensional ◽  
Tilted Magnetic Field

Abstract Surface quantum states in quasi-two dimensional organic conductors induced by an external magnetic field tilted in the plane of the layers are obtained and analyzed. In tilted magnetic fields, these states arise from the transitions of the electrons between the closed orbits on the sides of the Fermi surface determined by the electron momentum along the magnetic field direction p B and the coordinate of the center of electron revolution Z. By far, in organic conductors, the surface states have not been studied for tilted magnetic fields. In this work, we have performed detail analyses of the surface states in a tilted in-plane magnetic field by calculating the surface energy spectrum and surface wave functions in order to address their properties and features. We find that, in a tilted magnetic field, the surface levels have higher energies compared to those at zero tilt angle but can be observed only up to a certain tilt angle. The resonant magnetic field and angular values at which the peaks in the surface oscillations should be observed are obtained. Further theoretical and new experimental studies of the surface states in a tilted magnetic field might give new insights into the surface properties of quasi-two dimensional organic conductors. Additionally, they may reveal new information about the parameters of the Fermi surface of organic conductors necessary for its reconstruction.

Diamond CVD Growth Mechanisms and Reaction Rates From First-Principles

2000 ◽  
Vol 616 ◽  
Author(s):  
I.I Oleinik ◽  
D.G. Pettifor ◽  
A.P. Sutton ◽  
C.C. Battaile ◽  
D.J. Srolovitz ◽  
...  
Keyword(s):  
Monte Carlo ◽  
First Principles ◽  
Kinetic Monte Carlo ◽  
Experimental Studies ◽  
Cvd Diamond ◽  
Reaction Rates ◽  
Diamond Growth ◽  
Growth Mechanisms ◽  
Monte Carlo Studies ◽  
Cvd Growth

AbstractCVD diamond is an enabling material for diverse applications. In recent years, multiscale modelling of CVD growth in conjunction with experimental studies of the deposition processes has made a substantial progress towards our understanding of the fundamental growth chemistry and material quality. Macroscopic gas phase simulations of the CVD reactor, the mesoscale kinetic Monte-Carlo (KMC) modelling of the crystal growth and nanoscale modelling of the surface chemistry are three main legs in the multiscale hierarchy. In the framework of this methodology we have performed first-principles quantum mechanical calculations of bonding and reaction kinetics of the elementary growth processes and provided critical input in the form of atomistic growth mechanisms and reaction rates for the mesoscale KMC modelling of CVD diamond growth. A key success was achieved by combining first-principles and Monte Carlo studies to elucidate (100) growth mechanisms that have perplexed the diamond growth community for many years.

Simulations of Anisotropic Texture Evolution on Paramagnetic and Diamagnetic Materials Subject to a Magnetic Field Using Q-State Monte Carlo

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
J. B. Allen
Keyword(s):  
Magnetic Field ◽  
Monte Carlo ◽  
External Magnetic Field ◽  
Grain Boundary ◽  
Boundary Energy ◽  
Magnetic Field Direction ◽  
Grain Boundary Energy ◽  
Average Grain Size ◽  
Principal Axes ◽  
The Magnetic Field

The present work incorporates a modified Q-state Monte Carlo (Potts) model to evaluate two-dimensional annealing of representative paramagnetic and diamagnetic polycrystalline materials in the presence of a magnetic field. Anisotropies in grain boundary energy, caused by differences in grain orientation (texturing), and the presence of an external magnetic field are examined in detail. In the former case, the Read–Shockley equations are used, in which grain boundary energies are computed using a low-angle misorientation approximation. In the latter case, magnetic anisotropy is simulated based on the relative orientation between the principal grain axis and the external magnetic field vector. Among other findings, the results of texture development subject to a magnetic field showed an increasing orientation distribution function (ODF) asymmetry over time, with higher intensities favoring the grains with principal axes most closely aligned with the magnetic field direction. The magnetic field also tended to increase the average grain size, which was accompanied by a corresponding decrease in the total grain boundary energy.

Porous Aluminophosphates as Adsorbents for the Separation of CO2/CH4 and CH4/N2 Mixtures – a Monte Carlo Simulation Study

2018 ◽  
Author(s):  
Michael Fischer
Keyword(s):  
Monte Carlo ◽  
Landfill Gas ◽  
Experimental Studies ◽  
Chem Phys ◽  
Monte Carlo Simulation Study ◽  
Mixture Adsorption ◽  
Vacuum Swing Adsorption ◽  
Separation Of Co2 ◽  
Pressure Swing ◽  
Gcmc Simulations

<div>Aluminophosphates with zeolite-like topologies (AlPOs) have received considerable attention as potential adsorbents for use in the separation of methane-containing gas mixtures. Such separations, especially the removal of carbon dioxide and nitrogen from methane, are of great technological relevance in the context of the “upgrade” of natural gas, landfill gas, and biogas. While more than 50 zeolite frameworks have been synthesised in aluminophosphate composition or as heteroatom substituted AlPO derivatives, only a few of them have been characterised experimentally with regard to their adsorption and separation behaviour. In order to predict the potential of a variety of AlPO frameworks for applications in CO<sub>2</sub>/CH<sub>4</sub> and CH<sub>4</sub>/N<sub>2</sub> separations, atomistic grand-canonical Monte Carlo (GCMC) simulations were performed for 53 different structures. Building on previous work, which studied CO<sub>2</sub>/N<sub>2</sub> mixture adsorption in AlPOs (M. Fischer, <i>Phys. Chem. Chem. Phys.</i>, 2017, <b>19</b>, 22801–22812), force field parameters for methane adsorption in AlPOs were validated through a comparison to available experimental adsorption data. Afterwards, CO<sub>2</sub>/CH<sub>4</sub> and CH<sub>4</sub>/N<sub>2</sub> mixture isotherms were computed for all 53 frameworks for room temperature and total pressures up to 1000 kPa (10 bar), allowing the prediction of selectivities and working capacities for conditions that are relevant for pressure swing adsorption (PSA) and vacuum swing adsorption (VSA). For CO<sub>2</sub>/CH<sub>4 </sub>mixtures, the <b>GIS</b>, <b>SIV</b>, and <b>ATT</b> frameworks were found to have the highest selectivities and CO<sub>2 </sub>working capacities under VSA conditions, whereas several frameworks, among them <b>AFY</b>, <b>KFI</b>, <b>AEI</b>, and <b>LTA</b>, show higher working capacities under PSA conditions. For CH<sub>4</sub>/N<sub>2</sub> mixtures, all frameworks are moderately selective for methane over nitrogen, with <b>ATV</b> exhibiting a significantly higher selectivity than all other frameworks. While some of the most promising topologies are either not available in pure-AlPO<sub>4</sub> composition or collapse upon calcination, others can be synthesised and activated, rendering them interesting candidates for future experimental studies. In addition to predictions of mixture adsorption isotherms, further simulations were performed for four selected systems in order to investigate the microscopic origins of the macroscopic adsorption behaviour, <i>e.g. </i>with regard to the very high CH<sub>4</sub>/N<sub>2</sub> selectivity of <b>ATV</b> and the loading-dependent evolution of the heat of CO<sub>2</sub> adsorption and CO<sub>2</sub>/CH<sub>4</sub> selectivity of <b>AEI</b> and GME.</div>

Monte Carlo calculation of the energy parameters and spatial distribution of the cathodic arc ions while passing through the macro-particles filters

2018 ◽  
Vol 1 (1) ◽  
pp. 30-34 ◽  
Author(s):  
Alexey Chernogor ◽  
Igor Blinkov ◽  
Alexey Volkhonskiy
Keyword(s):  
Magnetic Field ◽  
Mass Transfer ◽  
Monte Carlo ◽  
Monte Carlo Calculation ◽  
Inhomogeneous Magnetic Field ◽  
Flow Energy ◽  
Wide Range ◽  
Field Concentrator ◽  
Cathodic Arc ◽  
The Magnetic Field

The flow, energy distribution and concentrations profiles of Ti ions in cathodic arc are studied by test particle Monte Carlo simulations with considering the mass transfer through the macro-particles filters with inhomogeneous magnetic field. The loss of ions due to their deposition on filter walls was calculated as a function of electric current and number of turns in the coil. The magnetic field concentrator that arises in the bending region of the filters leads to increase the loss of the ions component of cathodic arc. The ions loss up to 80 % of their energy resulted by the paired elastic collisions which correspond to the experimental results. The ion fluxes arriving at the surface of the substrates during planetary rotating of them opposite the evaporators mounted to each other at an angle of 120° characterized by the wide range of mutual overlapping.

A 3 T superconducting magnet for long-run magnetic Compton-scattering experiments

1998 ◽  
Vol 5 (3) ◽  
pp. 937-939 ◽  
Author(s):  
Nobuhiko Sakai ◽  
Hiroshi Ohkubo ◽  
Yasushi Nakamura
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Compton Scattering ◽  
Superconducting Magnet ◽  
Field Direction ◽  
Compton Profile ◽  
Magnetic Field Direction ◽  
Long Run ◽  
Radiation Shields ◽  
The Magnetic Field

A 3 T superconducting magnet has been designed and constructed for magnetic Compton-profile (MCP) measurements with the new capabilities that the magnetic field direction can be altered quickly (within 5 s) and liquid-He refill is not required for more than one week. For the latter capability, two refrigerators have been directly attached to the cryostat to maintain the low temperature of the radiation shields and for the recondensation of liquid He. The system has been satisfactorily operated for over one week.

scholarly journals Monte Carlo studies of pion distributions from heavy ion collisions

1983 ◽  
Vol 27 (2) ◽  
pp. 606-627 ◽  
Author(s):  
Hafez M. A. Radi ◽  
John O. Rasmussen ◽  
Kenneth A. Frankel ◽  
John P. Sullivan ◽  
H. C. Song
Keyword(s):  
Monte Carlo ◽  
Heavy Ion Collisions ◽  
Heavy Ion ◽  
Ion Collisions ◽  
Monte Carlo Studies

scholarly journals Enhanced X-ray emission arising from laser-plasma confinement by a strong transverse magnetic field

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Evgeny D. Filippov ◽  
Sergey S. Makarov ◽  
Konstantin F. Burdonov ◽  
Weipeng Yao ◽  
Guilhem Revet ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Transverse Magnetic ◽  
Radiative Properties ◽  
Magnetic Field Direction ◽  
Solid Target ◽  
Total Plasma ◽  
Plasma Confinement ◽  
X Ray ◽  
Magnetic Compression ◽  
The Magnetic Field

AbstractWe analyze, using experiments and 3D MHD numerical simulations, the dynamic and radiative properties of a plasma ablated by a laser (1 ns, 10$$^{12}$$ 12 –10$$^{13}$$ 13 W/cm$$^2$$ 2 ) from a solid target as it expands into a homogeneous, strong magnetic field (up to 30 T) that is transverse to its main expansion axis. We find that as early as 2 ns after the start of the expansion, the plasma becomes constrained by the magnetic field. As the magnetic field strength is increased, more plasma is confined close to the target and is heated by magnetic compression. We also observe that after $$\sim 8$$ ∼ 8  ns, the plasma is being overall shaped in a slab, with the plasma being compressed perpendicularly to the magnetic field, and being extended along the magnetic field direction. This dense slab rapidly expands into vacuum; however, it contains only $$\sim 2\%$$ ∼ 2 % of the total plasma. As a result of the higher density and increased heating of the plasma confined against the laser-irradiated solid target, there is a net enhancement of the total X-ray emissivity induced by the magnetization.

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