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排序方式: 共有58条查询结果,搜索用时 15 毫秒
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Some aspects of resonant vibrations of self-interstitials in the 100-dumbbell configuration are discussed by using a simple defect model incorporating nearest-neighbour interactions, with parameters fitted to the results of computer simulation. Especially we calculate the change of the lattice specific heat due to interstitials. An appreciable increase of the specific heat is obtained yielding a peak at 9–10 K in C/C for Cu. Following a recent suggestion of W. Schilling the diffuse inelastic one-phonon scattering is calculated in the range of the resonance frequencies forq-values away from the phonon-line. In particular, an appreciable diffuse intensity is obtained for theE
g-mode making an experimental observation by neutron scattering feasible. 相似文献
4.
Using the method of Hill a variational principle is derived to obtain upper and lower bounds for the effective elastic constants of disordered materials, such as polycrystals or multiphase materials. All bounds previously known are rederived and especially new bounds are given being closer than the ones of Hashin and Shtrikman. In detail the elastic constants of polycrystals built of cubic single crystals and of multiphase materials are considered. The analogous bounds for the dielectric constant of polycrystals are also given. 相似文献
5.
Nonas B Cabria I Zeller R Dederichs PH Huhne T Ebert H 《Physical review letters》2001,86(10):2146-2149
We present ab initio calculations for orbital moments and anisotropy energies of 3d and 5d adatoms on the Ag(001) surface, based on density functional theory, including Brooks' orbital polarization (OP) term, and applying a fully relativistic Korringa-Kohn-Rostoker-Green's function method. In general, we find unusually large orbital moments and anisotropy energies, e.g., in the 3d series, 2.57 mu(B) and +74 meV for Co, and, in the 5d series, 1.78 mu(B) and +42 meV for Os. These magnetic properties are determined mainly by the OP and even exist without spin-orbit coupling. 相似文献
6.
Schmidt M Theissen P Deutsch HJ Dederichs B Franzen D Erdmann E Schicha H 《Magnetic resonance imaging》2000,18(4):417-422
Diagnosis of congenitally corrected transposition of the great arteries (L-TGA) with situs inversus totalis in two adult patients was made by magnetic resonance imaging (MRI). Visualization of the complete anatomy and quantification of ventricular function was possible. Relevant concomitant disease such as perimembraneous ventricular septal defect, atrial secundum septal defect, tricuspid regurgitation, valvular pulmonic stenosis, and pulmonary artery dilatation were clearly depicted by MRI using standard spin-echo and gradient-echo techniques. Findings were confirmed by cardiac catheterization in both patients. In this rare and complex congenital cardiac anomaly, MRI is an excellent imaging modality as echocardiography may be difficult to interpret due to restricted imaging windows. MRI may help in the decision about the necessity to undergo further invasive evaluation and may help to make cardiac catheterization a straightforward procedure. 相似文献
7.
S. Papp L. Kőrösi B. Gool T. Dederichs P. Mela M. Möller I. Dékány 《Journal of Thermal Analysis and Calorimetry》2010,101(3):865-872
Gold nanoparticles (Au NPs) were prepared by the reduction of HAuCl4 acid incorporated into the polar core of poly(styrene)-block-poly(2-vinylpyridine) (PS-b-P2VP) copolymer micelles dissolved in toluene. The formation of Au NPs was controlled using three reducing agents with different
strengths: hydrazine (HA), triethylsilane (TES), and potassium triethylborohydride (PTB). The formation of Au NPs was followed
by transmission electron microscopy, UV–Vis spectroscopy, isothermal titration calorimetry (ITC), and dynamic light scattering
(DLS). It was found that the strength of the reducing agent determined both the size and the rate of formation of the Au NPs.
The average diameters of the Au NPs prepared by reduction with HA, TES, and PTB were 1.7, 2.6, and 8 nm, respectively. The
reduction of Au(III) was rapid with HA and PTB. TES proved to be a mild reducing agent for the synthesis of Au NPs. DLS measurements
demonstrated swelling of the PS-b-P2VP micelles due to the incorporation of HAuCl4 and the reducing agents. The original micellar structure rearranged during the reduction with PTB. ITC measurements revealed
that some chemical reactions besides Au NPs formation also occurred in the course of the reduction process. The enthalpy of
formation of Au NPs in PS-b-P2VP micelles reduced by HA was determined. 相似文献
8.
I. Turek J. Kudrnovský V. Drchal P. Weinberger P. H. Dederichs 《Journal of magnetism and magnetic materials》2002,240(1-3):162-164
The electronic structure and the residual resistivity of random FeRh-based alloys in the CsCl structure are calculated for different spin configurations using the tight-binding linear muffin–tin orbital method. The effect of substitutional impurities (Pd, Rh) is described by means of the coherent potential approximation. It is shown that impurity scattering leads to giant magnetoresistance effects in qualitative agreement with experiment. 相似文献
9.
P. H. Dederichs 《Zeitschrift für Physik B Condensed Matter》1966,5(5):347-363
The temperature dependence of dynamical crystal-interferences is investigated. The elastic scattering component is determined by a temperature and energy dependent optical potential analogous to nuclear physics. In a first approximation the optical potential is given by the thermal average of the crystal potential. The deviation depends on the pair density of the crystal atoms. The influence on absorption is evaluated employing approximations for the pair density. 相似文献
10.
V.S. Stepanyuk D.I. Bazhanov A.N. Baranov W. Hergert A.A. Katsnelson P.H. Dederichs J. Kirschner 《Applied Physics A: Materials Science & Processing》2001,72(4):443-446
Structural relaxations in small Co islands on the Cu(001) surface are investigated performing atomistic calculations. We demonstrate
that the strain relief at the metal interface in the early stages of heteroepitaxy is more complicated than suggested by simple
considerations based on the small mismatch between the Co and Cu bulk metals. We found that the strain distribution in the
surface region near the islands varies strongly on an atomic scale. The effect of strain on the shape of the Co islands is
revealed. Diffusion on the top of strained islands and edge diffusion are considered.
Received: 10 April 2000 / Accepted: 15 May 2000 / Published online: 7 March 2001 相似文献