Physica Status Solidi (B): Basic Research
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Performance of scintillation materials at cryogenic temperatures
Physica Status Solidi (B): Basic Research - Tập 247 Số 7 - Trang 1583-1599 - 2010
Magnetic Properties of Pd<sub>3</sub>Fe Abstract The Stoner model of ferromagnetism in combination with self‐consistent linear muffin‐tin paramagnetic calculations are used for the investigation of magnetic properties of the Pd3 Fe compound. Very good agreement is obtained with previous more complicated spin‐polarized calculations and experiments.
Physica Status Solidi (B): Basic Research - Tập 160 Số 2 - Trang 635-640 - 1990
The Temperature Dependence of the Domain Structure of Magnetoplumbite Abstract A study is made of the influence of temperature on the domain structure of magnetoplumbite, the domains being observed by the use of the Faraday effect. The temperature dependence of the width of the equilibrium domains is measured from −150° to + 380 °C, and used to calculate the temperature dependence of the exchange constant. The effect of the thermal hysteresis of the domain structure is investigated and discussed qualitatively.
Physica Status Solidi (B): Basic Research - Tập 3 Số 11 - Trang 2015-2028 - 1963
Auxetic behaviour from rotating rhombi Abstract Auxeticity (i.e. negative Poisson's ratios) is associated with particular geometrical features and deformation mechanisms of a system. Among the potential systems that may exhibit such behaviour are rotating rigid units. Here we discuss how rigid rhombi of the same shape and size can be connected in two different ways to give rise to two distinct systems: the Type α and Type β rotating rhombi. We derive the mechanical properties, for the Type β system and compare it to those of the Type α to highlight the differences between the two systems namely that Type α systems are highly anisotropic and can exhibit both negative and positive Poisson's ratios which depend on the shape of the rhombi and the angle between them whereas Type β systems are isotropic with a constant in‐plane Poisson's ratio of –1. Furthermore we show that by constructing the rhombi from five truss‐type elements, where the one forming the diagonal has a different thermal expansion than the other four identical trusses, the Poisson's ratios for the Type α systems can also be made temperature dependent, in contrast with Type β systems which remain unaffected by temperature changes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Physica Status Solidi (B): Basic Research - Tập 245 Số 11 - Trang 2395-2404 - 2008
A three‐dimensional rotating rigid units network exhibiting negative Poisson's ratios Abstract Materials exhibiting auxetic behaviour get fatter when stretched (i.e. possess a negative Poisson's ratio). This property has been closely related to particular geometrical features of a system and how it deforms. One of the mechanisms which is known to have a potential to generate such behaviour is that of rotating rigid units. Several models based on this concept have been developed, including two‐dimensional as well as three‐dimensional (3D) models. In this work, we propose a new 3D structure constructed from rigid cuboids which also deform through relative rotation of the units. In particular, analytical models for the mechanical properties, namely the Poisson's ratio and the Young's moduli, are derived and it is shown that for loading on‐axis, these systems have the potential to exhibit negative values for all the six on‐axis Poisson's ratios.
Physica Status Solidi (B): Basic Research - Tập 249 Số 7 - Trang 1330-1338 - 2012
Auxetic behaviour from rotating rigid units Abstract Auxetic materials exhibit the unexpected feature of becoming fatter when stretched and narrower when compressed, in other words, they exhibit a negative Poisson's ratio. This counter‐intuitive behaviour imparts many beneficial effects on the material's macroscopic properties that make auxetics superior to conventional materials in many commercial applications. Recent research suggests that auxetic be‐haviour generally results from a cooperative effect between the material's internal structure (geometry setup) and the deformation mechanism it undergoes when submitted to a stress. Auxetic behaviour is also known to be scale‐independent, and thus, the same geometry/deformation mechanism may operate at the macro‐, micro‐ and nano‐ (molecular) level. A considerable amount of research has been focused on the ‘re‐entrant honeycomb structure’ which exhibits auxetic behaviour if deformed through hinging at the joints or flexure of the ribs, and it was proposed that this ‘re‐entrant’ geometry plays an impor‐ tant role in generating auxetic behaviour in various forms of materials ranging from nanostructured polymers to foams. This paper discusses an alternative mode of deformation involving ‘rotating rigid units’ which also results in negative Poisson's ratios. In its most ideal form, this mechanism may be construc‐ ted in two dimensions using ‘rigid polygons’ connected together through hinges at their vertices. On application of uniaxial loads, these ‘rigid polygons’ rotate with respect to each other to form a more open structure hence giving rise to a negative Poisson's ratio. This paper also discusses the role that ‘rotating rigid units’ are thought to have in various classes of materials to give rise to negative Poisson's ratios. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Physica Status Solidi (B): Basic Research - Tập 242 Số 3 - Trang 561-575 - 2005
Searching for auxetics with DYNA3D and ParaDyn Abstract We sought to simulate auxetic behavior by carrying out dynamic analyses of mesoscopic model structures. We began by generating nearly periodic cellular structures. Four‐node “Shell” elements and eight‐node “Brick” elements are the basic building blocks for each cell. The shells and bricks obey standard elastic‐plastic continuum mechanics. The dynamical response of the structures was next determined for a three‐stage loading process: (1) homogeneous compression; (2) viscous relaxation; (3) uniaxial compression. The simulations were carried out with both serial and parallel computer codes – DYNA3D and ParaDyn – which describe the deformation of the shells and bricks with a robust contact algorithm. We summarize the results found here. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Physica Status Solidi (B): Basic Research - Tập 242 Số 3 - Trang 585-594 - 2005
On the properties of real finite-sized planar and tubular stent-like auxetic structures
Physica Status Solidi (B): Basic Research - Tập 251 Số 2 - Trang 321-327 - 2014
Negative compressibility, negative Poisson's ratio, and stability Abstract The role of negative compressibility is considered in detail. Experimental observations of negative bulk modulus in pre‐strained foam are presented and interpreted. A constrained microscopic model which exhibits negative compressibility is proposed. Some other negative and counterintuitive properties of matter, like negative Poisson's ratio, negative thermal expansion, negative specific heat, and negative pressure are also discussed. A simple thermodynamic model with negative thermal expansion is presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Physica Status Solidi (B): Basic Research - Tập 245 Số 3 - Trang 545-551 - 2008
Overlap and Covalency Contribution to the Zero‐Field Splitting of S‐State Ions Abstract General formulation of overlap and covalency effects for parameters D , E in the spin‐Hamiltonian of S‐state ions using the independent bond approach is developed. The model may be applied to complexes with both arbitrary coordination number and positions of ligands. All local, nonlocal, and distant terms of spin‐spin and spin‐orbit interactions are computed and used both for comparison with previous works on the Mn2+ ion with fluorine ligands and for discussion of the origin of the parameter D of octahedral Mn2+ and Fe2+ ions in garnets. Some of the errors and improper approximations appearing in various papers are discussed.
Physica Status Solidi (B): Basic Research - Tập 73 Số 2 - Trang 575-586 - 1976
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