Hunting Magnetic Phases with Total-Energy Spin-Polarized Band Calculations

1985 ◽  
Vol 63 ◽  
Author(s):  
P. M. Marcus ◽  
V. L. Moruzzi ◽  
K. Schwarz
Keyword(s):  
Total Energy ◽  
Phase Diagrams ◽  
Energy Band ◽  
Spin Moment ◽  
Magnetic Phases ◽  
First Order ◽  
Spin Polarized ◽  
Volume Range

ABSTRACTComments are made on total energy band calculations as tools for exploring properties of solids; the importance of fixed spin moment calculations is noted. Use of energy - magnetisation curves to locate magnetic phases is described. Detailed results for fcc and bcc Co and Ni and phase diagrams on the magnetisation - volume plane exhibit two new phases for each metal and show that ferromagnetic fcc Co and bcc Ni break down at small volumes and make first order transitions to nonmagnetic phases in a metamagnetic volume range.

A Study of Epitaxial Films of Bcc Nickel on FE{001} with leed Intensity analysis and Total Energy Band Calculations

1986 ◽  
Vol 83 ◽  
Author(s):  
P. M. Marcus ◽  
V. L. Moruzzi ◽  
Z. Q. Wang ◽  
Y. S. Li ◽  
F. Jona
Keyword(s):  
Total Energy ◽  
Energy Band ◽  
Metastable Phase ◽  
Binding Energies ◽  
Gradual Change ◽  
Layer Spacing ◽  
Spin Polarized ◽  
Stable Substrate ◽  
Bulk Structure ◽  
Stable And Metastable Phases

ABSTRACTAnalysis of LEED intensities of thin films of Ni grown epitaxially on bcc Fe{001} establishes that the structure is bcc up to six layers, but with a contraction of 5% of the first layer spacing and expansion of 5% of the second layer spacing. At thicknesses above six layers there is a gradual change to a new surface and bulk structure with increasing disorder. Spin-polarized total-energy band calculations show that the bcc Ni film is stretched 1.4% from its equilibrium value and thereby changed from nonmagnetic to ferromagnetic. The calculated results on stable and metastable phases of Fe, Co, Ni and Cu show that the equilibrium lattice parameters and differences in binding energies favor mutual epitaxy for any bcc or fcc pair. There are six pairs in which a possible metastable phase is grown epitaxially on a stable substrate.

First order reversal curve investigation of the hard and soft magnetic phases of annealed CoFeCu nanowire arrays

2013 ◽  
Vol 429 ◽  
pp. 46-51 ◽  
Author(s):  
M. Almasi-Kashi ◽  
A. Ramazani ◽  
E. Golafshan ◽  
M. Arefpour ◽  
E. Jafari-Khamse
Keyword(s):  
Nanowire Arrays ◽  
Soft Magnetic ◽  
Magnetic Phases ◽  
First Order

Density functional theory calculations of atomic, electronic and thermodynamic properties of cubic LaCoO3and La1−xSrxCoO3surfaces

RSC Advances ◽  
2015 ◽  
Vol 5 (1) ◽  
pp. 760-769 ◽  
Author(s):  
Shuguang Zhang ◽  
Ning Han ◽  
Xiaoyao Tan
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Dft Calculations ◽  
Phase Diagrams ◽  
Thermodynamic Stability ◽  
Electronic Structures ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Spin Polarized

Spin-polarized DFT calculations were used to investigate the atomic, electronic structures of LaCoO3and La1−xSrxCoO3surfaces. The thermodynamic stability of these surfaces was analyzed with phase diagrams. Influence of Sr-doping was also examined.

scholarly journals Oscillations of skyrmion clusters in Co/Pt multilayer nanodots

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Felipe Tejo ◽  
Felipe Velozo ◽  
Ricardo Gabriel Elías ◽  
Juan Escrig
Keyword(s):  
Total Energy ◽  
Relaxation Process ◽  
Oscillation Frequency ◽  
Equilibrium Configuration ◽  
Core Radius ◽  
Damped Oscillations ◽  
Spin Polarized

Abstract In this work we study the oscillations of the skyrmion cores in a multilayer nanodot as a function of the number of skyrmions hosted in the system. When all the skyrmions in the nanodot have the same core radius, and after applying a perpendicular spin-polarized current, a relaxation process takes place towards an equilibrium configuration that is accompanied by coherent damped oscillations of the skyrmion cores, whose frequency depends on the number of skyrmions present in the nanodot. Additionally, we found that the oscillation frequency is directly related to the total energy of the system.

ZNandN-state Potts lattice gauge theories: Phase diagrams, first-order transitions,βfunctions, and1Nexpansions

1980 ◽  
Vol 22 (10) ◽  
pp. 2447-2464 ◽  
Author(s):  
J. B. Kogut ◽  
R. B. Pearson ◽  
J. Shigemitsu ◽  
D. K. Sinclair
Keyword(s):  
Phase Diagrams ◽  
Gauge Theories ◽  
First Order ◽  
Lattice Gauge ◽  
Lattice Gauge Theories

Global energetics of fast magnetic reconnection

1988 ◽  
Vol 40 (3) ◽  
pp. 505-515 ◽  
Author(s):  
M. Jardine ◽  
E. R. Priest
Keyword(s):  
Steady State ◽  
Total Energy ◽  
Second Order ◽  
Weakly Nonlinear ◽  
First Order ◽  
Weakly Nonlinear Theory ◽  
Special Cases ◽  
Pile Up ◽  
Different Types ◽  
Converging Flow

We examine the global energetics of a recent weakly nonlinear theory of fast steady-state reconnection in an incompressible plasma (Jardine & Priest 1988). This is itself an extension to second order of the Priest & Forbes (1986) family of models, of which Petschek-like and Sonnerup-like solutions are special cases. While to first order we find that the energy conversion is insensitive to the type of solution (such as slow compression or flux pile-up), to second order not only does the total energy converted vary but so also does the ratio of the thermal to kinetic energies produced. For a slow compression with a strongly converging flow, the amount of energy converted is greatest and is dominated by the thermal contribution, while for a flux pile-up with a strongly diverging flow, the amount of energy converted is smallest and is dominated by the kinetic contribution. We also find that the total energy flowing out of the downstream region can be increased either by increasing the external magnetic Mach number Me or the external plasma beta βe Increasing Me also enhances the variations between different types of solutions.

Advances in Computation of Temperature-Pressure Phase Diagrams of High-Pressure Nitrides

2008 ◽  
Vol 403 ◽  
pp. 77-80 ◽  
Author(s):  
Peter Kroll
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Elevated Temperature ◽  
Total Energy ◽  
Phase Diagrams ◽  
High Pressures ◽  
First Principle ◽  
Energy Calculations ◽  
High Pressure High Temperature ◽  
Pressure Phase

A combination of first-principle and thermochemical calculations is applied to compute the phase diagrams of rhenium-nitrogen and of ruthenium-nitrogen at elevated temperature and high pressure. We augment total energy calculations with our approach to treat the nitrogen fugacity at high pressures. We predict a sequential nitridation of Re at high-pressure/high-temperature conditions. At 3000 K, ReN will form from Re and nitrogen at about 32 GPa. A ReN2 with CoSb2-type structure may be achieved at pressures exceeding 50 GPa at this temperature. Marcasite-type RuN2 will be attainable at 3000 K at pressures above 30 GPa by reacting Ru with nitrogen.

VOLUME DEPENDENCE OF VANADIUM MAGNETISM

1993 ◽  
Vol 07 (24n25) ◽  
pp. 1611-1618
Author(s):  
M.E. ELZAIN
Keyword(s):  
Crystal Size ◽  
Local Density ◽  
Magnetic Hyperfine Field ◽  
Local Magnetic Moment ◽  
General Shape ◽  
First Order ◽  
Atom Clusters ◽  
Discrete Variational Method ◽  
Spin Polarized ◽  
Local Properties

The first principle discrete variational method in the spin polarized local density approximation is used to calculate the local properties of 15 atom clusters representing variable crystal size bcc vanadium. Four distinct magnetic configurations are recognized as the lattice constant varies from 5.4 to 8.4 (a.u). At the lowest end, the clusters are paramagnetic (PM) whereas at the upper end, clusters are ferromagnetic (FM). In between, antiferromagnetic couplings prevail. The local magnetic moment increases, in a fashion not unlike second order transitions, from zero in the PM range to nonzero in the AFM region. Transitions between other phases are first order. The systematics of these transitions are ascribed to the general shape of the density of states. The contact magnetic hyperfine field, charge density, and 3d partial occupations at the central sites are also calculated.

Stabilization of a CSTR in an Oscillatory State by Varying the Thermal Characteristics of the Reactor Vessel

2006 ◽  
Vol 4 (1) ◽  
Author(s):  
Luis F Razon
Keyword(s):  
Phase Diagrams ◽  
Limit Cycle ◽  
Bifurcation Analysis ◽  
Chemical Engineering ◽  
Exothermic Reaction ◽  
Thermal Characteristics ◽  
Reactor Vessel ◽  
First Order ◽  
Classic Problem ◽  
Oscillatory State

One of the most thoroughly studied systems in chemical engineering is the classic problem of a first-order exothermic reaction in a diabatic CSTR. In this paper, an extension of the classic problem, in which the reactor vessel temperature varies independently of its contents, is considered. A bifurcation analysis showed that a CSTR in an oscillatory state may be stabilized by the use of a reactor with the appropriate combination of thermal characteristics. Stabilization of an oscillatory state was demonstrated for a variety of scenarios that had been previously shown by Uppal, Ray and Poore to be representative cases of phase diagrams that exhibit limit-cycle behavior.

Cohesion, Compound Formation and Phase Diagrams from First Principles

1982 ◽  
Vol 19 ◽  
Author(s):  
A. R. Williams ◽  
C. D. Gelatt ◽  
J. W. D. Connolly ◽  
V. L. Moruzzi
Keyword(s):  
Transition Metal ◽  
Phase Diagrams ◽  
First Principles ◽  
Formation Process ◽  
Energy Band ◽  
Empirical Formula ◽  
Heats Of Formation ◽  
Disordered Materials ◽  
Compound Formation ◽  
Self Consistent

ABSTRACTThe physical picture of cohesion and compound formation provided by parameter-free, self-consistent, energy-band calculations will be described. For transition-metal elements, the calculations allow us to “see” which electrons are holding the solid together and which are holding it apart. For compounds, calculated heats of formation agree well with available measurements and are in general agreement with those given by Miedema's empirical formula. (The agreement with Miedema is paradoxical, in that Miedema's conception of the formation process differs qualitatively from ours.) Preliminary, but very encouraging, results of efforts to extend the analysis to disordered materials and to the calculation of phase diagrams are described.

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