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Theoretical Study on the Spin-State Transition of Electron-Doped Sr_2-x La _x CoO₄ Compounds

JOURNAL OF LOW TEMPERATURE PHYSICS 2013年第1-2期171卷 77-86页

作者： Zhang, Xiu'e Kang, Yonggang Inst Disaster Prevent Sanhe 06520 Hebei Peoples R China

The spin-state transition is an interesting and unresolved problem in layered perovskite Sr2-x La (x) CoO4 under doping. The unrestricted Hartree-Fock approximation on a realistic multiband lattice model has been applied to study the various spin states of electron-doped Sr2-x La (x) CoO4 compounds. In the doping range 0.0a parts per thousand currency signxa parts per thousand currency sign0.9, various spin states in an enlarged double cell are investigated and four of them are the ground states at different doping concentration. The magnetic ground state of the doped system takes a low-spin-intermediate-spin ferromagnetically ordered state for x < 0.26, a high-spin-intermediate-spin ferromagnetically ordered state for 0.26a parts per thousand currency signx < 0.47, an intermediate-spin state for 0.47a parts per thousand currency signx < 0.65, and followed by an high-spin antiferromagnetically ordered state for 0.65a parts per thousand currency signxa parts per thousand currency sign0.9. The densities of states of all magnetic ground states are computed and their electronic and magnetic properties are discussed.

关键词： recursion method Hartree-Fock approximation Density of state Doping concentration Layered perovskite Magnetic ground state

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Nuclear spin-lattice relaxation at field-induced level crossings in a Cr₈F₈ pivalate single crystal

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PHYSICA B-CONDENSED MATTER 2016年 481卷 224-231页

作者： Yamamoto, Shoji Hokkaido Univ Dept Phys Sapporo Hokkaido 0600810 Japan

We construct a microscopic theory for the proton spin-lattice relaxation-rate 1/T-1 measurements around field-induced level crossings in a single crystal of the trivalent chromium ion wheel complex [Cr8F8(OOCtBu)(16)] at sufficiently low temperatures [E. Micotti et al., Phys. Rev. B 72 (2005) 020405(R)]. Exactly diagonalizing a well-equipped spin Hamiltonian for the individual clusters and giving further consideration to their possible interactions, we reveal the mechanism of 1/T-1] being single-peaked normally at the first level crossing but double-peaked intriguingly around the second level crossing. We wipe out the doubt about poor crystallization and find out a solution intramolecular alternating Dzyaloshinsky-Moriya interaction combined with intermolecular coupling of antiferromagnetic character, each of which is so weak as several tens of mK in magnitude. (C) 2015 Elsevier B.V. All rights reserved.

关键词： Molecular ring antiferromagnet Field-induced level crossing Nuclear spin-lattice relaxation recursion method Lanczos algorithm

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On the localization of electron states near silver ion adsorbed on atomic-rough surface of AgCl nanocrystal

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SURFACE SCIENCE 2009年第16期603卷 2564-2573页

作者： Timoshenko, Yury K. Shunina, Valentina A. Voronezh State Univ Dept Phys Voronezh 394006 Russia

Local partial and total densities of states for AgCl nanocrystals with the adsorbed silver ion were calculated by semi-empirical tight-binding method relying on a self-consistent approach for the effective charges and dipole moments of the ions. Adsorption was considered as on the atomically-rough surface (near the step and step fracture) as on the smooth surface. Visualization of the wave functions was performed for the localized states. Basing on the obtained data a conclusion is specifically made that one can expect an enhancement of photoelectron localization with a decrease of the anions number in the substrate nearest to the adsorbed ion. It means that the most efficient trapping of photoelectron should occur under adsorption on a smooth surface rather than near the steps and their fractures as it was assumed previously. (c) 2009 Elsevier B.V. All rights reserved.

关键词： Localized electron states AgCl nanocrystals Atomic-rough surface Adsorbed silver ion Tight-binding method recursion method Visualization of the wave functions Density functional theory

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A RECURSIVE method FOR FINDING REVOLUTE-JOINTED MANIPULATOR SINGULARITIES

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JOURNAL OF MECHANICAL DESIGN 1995年第1期117卷 55-63页

作者： BURDICK, JW Dept. of Mechanical Engineering California Institute of Technology Pasadena CA 91125

A geometric application of screw theory is used to develop a recursive algorithm for computing all singular configurations of revolute-jointed manipulators with arbitrary link geometries and an arbitrary number of joints. The depth of the recursion is linear in the number of joints, n, while the computational burden is proportional to 2n-2. This method does not require explicit construction of the Jacobian matrix elements or a determinant operation. The method is also robust with respect to the bifurcations that occur for industrial robot geometries. Further, the screw axis of the singular motion is determined at no additional cost.

关键词： Singularity BIFURCATION screw axis recursion method Recursive algorithms Singular Proportional Joints industrial robots Arbitrary Jacobian matrix Matrix Element

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Harmonic inversion of time signals and its applications

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JOURNAL OF CHEMICAL PHYSICS 1997年第17期107卷 6756-6769页

作者： Mandelshtam, VA Taylor, HS UNIV SO CALIF DEPT CHEM LOS ANGELES CA 90089 USA

New methods of high resolution spectral analysis of short time signals are presented. These methods utilize the filter-diagonalization approach of Wall and Neuhauser [J. Chem. Phys. 102, 8011 (1995)] that extracts the complex frequencies omega(k) and amplitudes d(k) from a signal C(t)=Sigma(k)d(k)e-(it omega k) in a small frequency interval by recasting the harmonic inversion problem as the one of a small matrix diagonalization. The present methods are rigorously adapted to the conventional case of the signal available on a sparse equidistant time grid and use a more efficient boxlike filter. Various applications are discussed, such as iterative diagonalization of large Hamiltonian matrices for calculating bound and resonance states, scattering calculations in the presence of narrow resonances, etc. For the scattering problem the harmonic inversion is directly applied to the signal c(n)=(chi(f), T-n((H) over cap)chi(i)), generated by the dynamical system governed by a modified Chebyshev recursion, avoiding the usual recasting the problem to the time domain. Some challenging numerical examples are presented. The general filter-diagonalization method is shown to be stable and efficient for the extraction of thousands of complex frequencies omega(k) and amplitudes d(k) from a signal. When the model signal is ''spoiled'' by a moderate amount of an additive Gaussian noise the obtained spectral estimate is still superior to the conventional Fourier spectrum. (C) 1997 American Institute of Physics. [S0021-9606(97)02541-5].

关键词： spectral analysis vibrational states bound states resonant states Chebyshev approximation recursion method

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AN ADAPTIVE PLASMA-GLUCOSE CONTROLLER BASED ON A NONLINEAR INSULIN/GLUCOSE MODEL

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IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING 1994年第2期41卷 116-124页

作者： CANDAS, B RADZIUK, J OTTAWA CIVIC HOSP DIABET & METAB RES UNITOTTAWA K1Y 4E9ONCANADA UNIV OTTAWA OTTAWAONCANADA

The design of plasma glucose controllers traditionally relies on linear approaches. The implementation of an appropriate nonlinear model of the insulin/glucose regulatory system into an adaptive controller should predict the insulin-dependent glucose removal more reliably and hence provide better control over a wide spectrum of insulin signals. A discretized form of the model leads to a two-step procedure. First, the measured plasma glucose levels associated with the exogenous glucose infusion rates are used in the estimation of the past removal rates which, in turn, can be expressed as a weighted sum of past insulin inputs and previous values of the removal rate. Parameters of the sum are adjusted on-line by a recursive method of estimation which features a prefiltering of data to account for a corrupting coloured process noise. The same equation is in turn used to predict the time course of the insulin-dependent fractional rate of glucose removal. The performance of the controller, tested in vivo in three pigs, is presented for various intravenous or subcutaneous rapid injections and staircase infusions of insulin. Plasma glucose is maintained at an average level of 99.9 +/- 8.7% of the target value (% set point +/- coefficient of variation). The controller reacts promptly to large and rapid variations in insulin action. Although control improves with the number of glucose measurements, the prediction of glucose removal allows for some flexibility in the monitoring of the plasma glucose. Sampling frequency varied from a 2 min interval during transient periods to 7 min as steady states were reached.

关键词： adaptive control biocontrol blood nonlinear control systems organic compounds patient treatment physiological models 2 min 7 min adaptive plasma glucose controller corrupting coloured process noise data prefiltering diabetes treatment erogeneous glucose Insulins organic compounds Blood Glucose recursion method Nonlinear control systems Controllers adaptive control patient treatment Insulin Prefiltration rapid variations Glucose physiological models Blood

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Bethe lattice consideration of the antiferromagnetic spin-1 Ising model

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PHYSICS LETTERS A 2004年第2-3期324卷 114-119页

作者： Ekiz, C Gaziosmanpasa Univ Dept Phys TR-60110 Tokat Turkey

The antiferromagnetic Blume-Capel spin-1 Ising model in an external magnetic field is considered on the Bethe lattice. Using an iteration technique, we obtain the plots of magnetization versus temperature for different external fields and construct the resulting phase diagrams. Comparison is made between the results of this study and previous mean-field and Monte Carlo simulations. It was found that the decomposition of the tricritical point into a critical end point and a critical point appears in the phase diagram for q = 6. (C) 2004 Elsevier B.V. All rights reserved.

关键词： Blume-Capel model Bethe lattice recursion method phase diagrams

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The importance of self-consistency in determining interface properties of SIN and DIN structures

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SUPERLATTICES AND MICROSTRUCTURES 1999年第5-6期25卷 1019-1031页

作者： Martin, AM Annett, JF Univ Geneva Dept Phys Theor CH-1211 Geneva 4 Switzerland Univ Bristol HH Wills Phys Lab Bristol BS8 1TL Avon England

We develop a method to solve the Bogoliubov-de Gennes equation for superconductors self-consistently, using the recursion method. The method allows the pairing interaction to be either local or nonlocal corresponding to s-and d-wave superconductivity, respectively. Using this method, we examine the properties of various SW and DIN interfaces. In particular, we self-consistently calculate the spatially varying density of states and the superconducting order parameter. We see that changing the strength of the insulating barrier at the interface, does not, in the case of an s-wave superconductor, dramatically change the low-energy local density of states in the superconducting region near the interface. This is in stark contrast to what we see in the case of a DIN interface where the local particle density of states is changed dramatically. Hence we deduce that in calculating such properties as the conductance of SIN and DIN structures it is far more important to carry out self-consistent calculations in the d-wave case. (C) 1999 Academic Press.

关键词： self-consistency interfaces d-wave order parameter recursion method superconductivity

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Real-space first-principles electronic structure of edge dislocations: NiAl

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PHILOSOPHICAL MAGAZINE LETTERS 1998年第5期78卷 427-433页

作者： Kontsevoi, OY Mryasov, ON Gornostyrev, YN Freeman, AJ Katsnelson, MI Trefilov, AV Northwestern Univ Dept Phys & Astron Evanston IL 60208 USA Inst Solid State Chem Ekaterinburg 620219 Russia Inst Met Phys Ekaterinburg 620219 Russia Kurchatov Inst Russian Sci Ctr Moscow 123182 Russia

The electronic structure of the [100]{010} edge dislocation in NiAl has been calculated using the real-space tight-binding linear muffin-tin orbital recursion method with a self-consistent treatment of electron density redistribution effects in the dislocation core. We demonstrate that quasilocalized states may exist in this metallic system as a result of specific lattice distortions in the dislocation core with 'broken bonds'.

关键词： recursion method edge dislocations Electron density dislocation core BREAKS Electronic structure

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The rheology of hard sphere suspensions at arbitrary volume fractions: An improved differential viscosity model

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JOURNAL OF CHEMICAL PHYSICS 2009年第4期130卷 044904-1-044904-7页

作者： Mendoza, Carlos I. Santamar-a-Holek, I. Univ Nacl Autonoma Mexico Inst Invest Mat Fac Ciencias Mexico City 04510 DF Mexico

We propose a simple and general model accounting for the dependence of the viscosity of a hard sphere suspension at arbitrary volume fractions. The model constitutes a continuum-medium description based on a recursive-differential method where correlations between the spheres are introduced through an effective volume fraction. In contrast to other differential methods, the introduction of the effective volume fraction as the integration variable implicitly considers interactions between the spheres of the same recursive stage. The final expression for the viscosity scales with this effective volume fraction, which allows constructing a master curve that contains all the experimental situations considered. The agreement of our expression for the viscosity with experiments at low- and high-shear rates and in the high-frequency limit is remarkable for all volume fractions.

关键词： recursion method rheology suspensions viscosity

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