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11.
We present a series of rigorous examples of the Kondo lattice model that exhibit full ferromagnetism in the ground state.
The models are defined in one-, two- and three-dimensional lattices, and are characterized by a range of hopping terms, specific
electron filling, and large ferromagnetic coupling. Our examples show that a sufficient strong but finite exchange coupling
between conduction electrons and localized spins could overcome the competition from mobility of a finite density of electrons
and drive the system from a paramagnetic phase to a ferromagnetic phase. We also establish a relation of ferromagnetism between
the Hubbard model and Kondo lattice model. Meanwhile some rigorous results on ferromagnetism in the corresponding Hubbard
model are presented.
Received: 10 September 1997 / Revised: 15 October 1997 / Accepted: 17 October 1997 相似文献
12.
Both alkane- and arene-sulfinates undergo racemization and oxygen exchange reaction with trich-loroacetic anhydride. The rate of racemization of (?)menthyl (?)p-toluenesulfinate was found to be twice that of oxygen exchange, suggesting the reaction involves a Walden inversion. When reaction was carried out in benzene, the rate of racemization was found to be first order with respect to both sulfinic ester and trichloroacetic anhydride. The substituent effect is large (p = ?1.53) suggesting that the initial acylation is the rate-determining step. The rate of racemization was found to be retarded by the addition of perhaloacetic acid while very small catalytic effect of mercuric chloride was observed. 相似文献
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14.
Summary Results are reported on near-i.r. absorption spectra of H2O and D2O down to the temperature region of supercooled liquid. No anomalous behaviour is observed when the absorbance at any given
frequency is studied as a function of temperature. A critical-exponent behaviour strikingly correlating with that exhibited
by transport properties is instead observed when spectral deconvolution methods are used. Results are discussed in relation
with current views on water structure, based on molecular-dynamics simulation results and connectivity calculations.
Riassunto Si riportano risultati sugli spettri di assorbimento i.r. di H2O e D2O fino alla regione di temperature del liquido sopraraffreddato. L'andamento dell'assorbanza a frequenza costante in funzione della temperatura non mostra alcuna indicazione di comportamento anomalo. Al contrario, quando gli spettri sono analizzati con metodo di deconvoluzione, si osserva un comportamento di tipo esponente critico, che correla straordinariamente bene con quello mostrato dalle proprietà di trasporto. I risultati sono discussi anche in relazione ai piú recenti modelli di struttura dell'acqua, derivanti dai risultati di simulazione e dai calcoli di connettività.
Резюме Приводятся результаты для спектров инфракрасного поглощения H2O и D2O для температур переохлажденной жидкости. Не обнаружено аномального поведения, когда поглощательная способность при заданной частоте изучается как функция темпетатуры. Напротив, при анализе спектров с помощью спектральных методов конволюции наблюдается поведение типа критической экспоненты, которое коррелирует с поведением, определяемым транспортыми свойствами. Полученные результаты обсуждаются в связи с недавними моделями структуры воды, полученными на основе моделирования молекулярной динамики и нычислений связности.相似文献
15.
R. Roldán A. Rüegg M. Sigrist 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,64(2):185-192
Metamagnetism in layered ruthenates has been interpreted as a novel kind of quantum critical behavior. In an external magnetic
field, Ca2-xSrxRuO4 undergoes a metamagnetic transition accompanied by a pronounced magnetostriction effect. In this paper we present a mean-field
study for a microscopic model that naturally reproduces the key features of this system. The phase diagram calculated is equivalent
to the experimental T-x phase diagram. The presented model also gives a good basis to discuss the critical metamagnetic behavior measured in the
system. 相似文献
16.
Han Wang Christoph Junghans Kurt Kremer 《The European physical journal. E, Soft matter》2009,28(2):221-229
We employ the inverse Boltzmann method to coarse-grain three commonly used three-site water models (TIP3P, SPC and SPC/E)
where one molecule is replaced with one coarse-grained particle with isotropic two-body interactions only. The shape of the
coarse-grained potentials is dominated by the ratio of two lengths, which can be rationalized by the geometric constraints
of the water clusters. It is shown that for simple two-body potentials either the radial distribution function or the geometrical
packing can be optimized. In a similar way, as needed for multiscale methods, either the pressure or the compressibility can
be fitted to the all atom liquid. In total, a speed-up by a factor of about 50 in computational time can be reached by this
coarse-graining procedure. 相似文献
17.
S. Ghosh B. Sanyal C.B. Chaudhuri A. Mookerjee 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(4):455-461
We study the electronic structure and magnetic properties of disordered bcc CoxFe1-x, CrxFe1-x and MnxFe1-x alloys in their ferromagnetic phases using the Augmented Space Recursion (ASR) technique coupled with the tight-binding linearized
muffin tin orbital (TB-LMTO) method. We calculate the density of states and magnetic moment of these alloys to show the variation
upon alloying Fe with the other neighbouring 3d transition metals using arguments based on charge transfer, exchange splitting and hybridization effects.
Received 10 April 2001 and Received in final form 15 August 2001 相似文献
18.
高功率速调管聚焦磁场设计研究 总被引:3,自引:1,他引:2
国产45 MW速调管是在原国产30 MW HK-1型速调管的基础上改进和发展起来的,其聚焦磁场设计也是参照30 MW速调管聚焦磁场设计并在其基础上加工改造完成。为此必须对旧聚焦系统进行改造,设计出符合需要的磁场分布,以满足45 MW速调管工作的需要。首先从理论上找出速调管工作时的理想磁场值,根据该磁场分布设计出相应的线圈结构;其次根据45 MW速调管的结构尺寸,对30 MW速调管的线圈支架进行改造,利用旧线圈和新支架组成新的聚焦系统;最后,根据理论模拟和测试结果,调整和优化各组线圈的电流值,给出速调管工作时的各组聚焦电源运行参考值。叙述了新聚焦线圈的理论设计和测试分析,包括新线圈支架的设计、水冷系统与线圈的结构安排和整体的测试结果,最后根据速调管高功率测试运行状态给出速调管工作时的聚焦线圈电流的参考值。 相似文献
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