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661.
Synthesis and Crystal Structure of the First Known Cp* Ligated Cobalt Telluride Cluster: Mild Oxidation of [Cp*CoCl]2 by Li4Sn2Te6 · 8 en to give [(Cp*Co)4(μ3‐Te)4] Oxidation of cobalt(II) complex [Cp*CoCl]2 (Cp* = pentamethylcyclopentadiene) with binary Zintl polyanion hexatellurodistannate(IV) [Sn2Te6]4– in Li4Sn2Te6 · 8 en (en = 1,2‐diaminoethane) leads to the formation of the first Cp* ligated cobalt telluride cluster [(Cp*Co)4(μ3‐Te)4]. The compound crystallizes as black cuboids that are suitable for X‐ray structural analysis. Space group P 1, lattice dimensions at 203 K: a = 1127.9(2), b = 1156.2(3), c = 1882.3(4) pm, α = 83.27(2), β = 83.24(2), γ = 66.11(1)°, V = 2222.3(9) · 106 pm3, R1 = 0.0681. The molecular structure of the compound features a Co4Te4 heterocubane and thus distributes to the completion of the series of known transition metal chalcogenide heterocubanes. 相似文献
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The method of reduced integration with hourglass stabilization is one of the most powerful techniques in the field of finite element technology. Caused by the use of a reduced number of integration points it leads to very efficient finite element formulations. To avoid the appearance of non-physical zero-energy modes an hourglass stabilization is necessary. This paper presents an adaptive hourglass stabilization strategy motivated by the hyperelastic formulation of finite inelasticity. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
664.
In this paper we suggest a new phenomenological material model for shape memory alloys. In contrast to many earlier concepts of this kind the present approach includes arbitrarily large deformations. The work is motivated by the requirement, also expressed by regulatory agencies, to carry out finite element simulations of NiTi stents. Depending on the quality of the numerical results it is possible to circumvent, at least partially, expensive experimental investigations. Stent structures are usually designed to significantly reduce their diameter during the insertion into a catheter. Thereby large rotations combined with moderate and large strains occur. In this process an agreement of numerical and experimental results is often hard to achieve. One of the reasons for this discrepancy is the use of unrealistic material models which mostly rely on the assumption of small strains. In the present paper we derive a new constitutive model which is no longer limited in this way. Further its efficient implementation into a finite element formulation is shown. One of the key issues in this regard is to fulfil “inelastic” incompressibility in each time increment. Here we suggest a new kind of exponential map where the exponential function is suitably computed by means of the spectral decomposition. A series expansion is completely avoided. Finite element simulations of stent structures show that the new concept is well appropriate to demanding finite element analyses as they occur in practically relevant problems. 相似文献
665.
Sheet metal forming simulations are increasingly replacing traditional build-and-break prototyping because they provide a less expensive and more rapid way to speed up product design time while improving quality and performance. Sheet metal is subjected to stretching, bending and unbending during forming, and an accurate prediction of the formability and springback of the sheet necessitates the use of an appropriate constitutive model. Use of isotropic hardening alone has been identified as a source of inaccurate springback prediction. In order to be able to describe the cyclic hardening behaviour and the Bauschinger effect, a large-deformation elasto-plastic material model with non-linear kinematic hardening is discussed in the present work. The model is derived from a thermodynamical framework and is based on the multiplicative split of the deformation gradient. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
666.
Hexapotassium Hexaselenodistannate(III) K6Sn2Se6 – Synthesis, Structure, and Properties of a New Salt-like SnIII Compound Reaction of stoichiometric amounts of potassium, tin, and selenium in sealed silica tubes yield at 900 °C K6Sn2Se6 ( 1 ) as red-orange solid of which small particles are very suitable for X-ray structural analysis. Space group P21/c, lattice dimensions at 203 K: a = 905.6(2), b = 1277.4(3), c = 888.7(2) pm, β = 115.86(3)°, R1 = 0.0332. Besides Cs6Sn2Se6, 1 represents the second hexaselenostannate(III) to be known and structurally characterized. Thus, it contributes to the completion of the hexachalcogenostannate(III) family. Additionally, 1 is isostructural and in some cases even isotypic to homologue compounds of the elements silicon and germanium. 相似文献
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