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Rijssenbeek JT Saito T Malo S Azuma M Takano M Poeppelmeier KR 《Journal of the American Chemical Society》2005,127(2):675-681
The related parameters of cation size and valence that control the crystallization of Sr(3)CaRu(2)O(9) into a 1:2 B-site-ordered perovskite structure were explored by cationic substitution at the strontium and calcium sites and by the application of high pressure. At ambient pressures, Sr(3)MRu(2)O(9) stoichiometries yield multiphasic mixtures for M = Ni(2+), Mg(2+), and Y(3+), whereas pseudocubic perovskites result for M = Cu(2+) and Zn(2+). For A-site substitutions, an ordered perovskite structure results for Sr(3-x)Ca(x)CaRu(2)O(9), with 0 = x = 1.5. In contrast, Ba(2+) substitution for Sr(2+) is accompanied by a phase change to a hexagonal BaTiO(3) structure type. At high pressures and temperatures, a 1:2 B-site-ordered perovskite structure is stabilized for Sr(3-x)Ba(x)CaRu(2)O(9), with 0 = x = 3. The scarcity of B-site-ordered perovskite ruthenates at ambient pressure and the metastable nature of the high-pressure phases underscore the strict size and valence requirements that must be met by the constituent cations to achieve these uncommon ordered structures. 相似文献
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Rijssenbeek JT Malo S Caignaert V Poeppelmeier KR 《Journal of the American Chemical Society》2002,124(10):2090-2091
Sr(3)CaRu(2)O(9), a new 2:1 B-site ordered perovskite ruthenate, was synthesized and its structure determined based on powder X-ray, neutron and electron diffraction data. It is composed of one layer of CaO(6) alternating with two layers of RuO(6) perpendicular to the [111] axis of the cubic perovskite structure. The ordering leads to a [-Ru-Ru-Ca-] repeat unit along each of the pseudocubic directions. Sr(3)CaRu(2)O(9) is the first example of this structure-type to include a majority metal with d electrons (Ru(V), d(3)). Three-dimensional Sr(3)CaRu(2)O(9) can be transformed to the layered Ruddlesden-Popper phase Sr(1.5)Ca(0.5)RuO(4) (i.e., Sr(3)CaRu(2)O(8)) by reduction at 1200 degrees C in flowing argon. The original structure can be restored by oxidation of Sr(1.5)Ca(0.5)RuO(4) at 1000 degrees C in flowing oxygen. This remarkable transformation highlights the structural versatility afforded by the combination of ruthenium and calcium. 相似文献
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G.W. van Apeldoorn D. Harting D.J. Holthuizen B.J. Pijlgroms M.M.H.M. Rijssenbeek V. Karimäki R. Kinnunen M. Korkea-Aho J. Maalampi J. Tuominiemi G.D. Patel P. Johnson P. Mason H. Muirhead B.M. Whyman 《Physics letters. [Part B]》1982,115(1):55-58
Data on the density of charged particles in rapidity space for annihilation and non-annihilation p?p interactions at 7.3 and 12 GeV/c are reported. It is shown that the central rapidity density for non-annihilation processes is a simple linear function of from these low energies up to p?p collider energies (). Significant differences in density distributions for p?p and e?e+ annihilations at comparable energies are found. 相似文献
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Soloveichik G Her JH Stephens PW Gao Y Rijssenbeek J Andrus M Zhao JC 《Inorganic chemistry》2008,47(10):4290-4298
The ammonia complex of magnesium borohydride Mg(BH4)2.2NH3 (I), which contains 16.0 wt % hydrogen, is a potentially promising material for hydrogen storage. This complex was synthesized by thermal decomposition of a hexaaammine complex Mg(BH4)2.6NH3 (II), which crystallizes in the cubic space group Fm3 m with unit cell parameter a=10.82(1) A and is isostructural to Mg(NH3) 6Cl2. We solved the structure of I that crystallizes in the orthorhombic space group Pcab with unit cell parameters a=17.4872(4) A, b=9.4132(2) A, c=8.7304(2) A, and Z=8. This structure is built from individual pseudotetrahedral molecules Mg(BH4)2.2NH3 containing one bidentate BH4 group and one tridentate BH4 group that pack into a layered crystal structure mediated by N-H...H-B dihydrogen bonds. Complex I decomposes endothermically starting at 150 degrees C, with a maximum hydrogen release rate at 205 degrees C, which makes it competitive with ammonia borane BH 3NH3 as a hydrogen storage material. 相似文献
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Computer simulations based on Discrete Element Method have been performed in order to investigate the influence of interparticle interactions on the kinetics of self-assembly and the mechanical strength of nanoparticle aggregates.Three different systems have been considered.In the first system the interaction between particles has been simulated using the JKR (Johnson,Kendall and Roberts) contact theory,while in the second and third systems the interaction between particles has been simulated using van der Waals and electrostatic forces respectively.In order to compare the mechanical behaviour of the three systems,the magnitude of the maximum attractive force between particles has been kept the same in all cases.However,the relationship between force and separation distance differs from case to case and thus,the range of the interparticle force.The results clearly indicate that as the range of the interparticle force increases,the self-assembly process is faster and the work required to produce the mechanical failure of the assemblies increases by more than one order of magnitude. 相似文献
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G. D. Patel P. Johnson P. Mason P. Michaelides C. Michaelidou H. Muirhead B. M. Whyman G. W. van Apeldoorn D. Harting D. J. Holthuizen B. J. Pijlgroms M. M. H. M. Rijssenbeek J. MacNaughton M. Markytan H. Rohringer L. Sakeliou G. Vassiliades S. Karpathopoulos M. Mermikides E. Zevgolatakos E. Katsoufis 《Zeitschrift fur Physik C Particles and Fields》1982,12(3):189-202
Absolute inclusive cross sections for \(\bar pp\) interactions at 7.3 GeV/c are given. The data cover prong cross sections,V 0, γ production and inclusive charged particle (p/π) production. Separation has been made into annihilation and non-annihilation components. Inclusive π+, π? production in the processes of \(\bar pp\) annihilation and non-annihilation are compared with simple quark models. 相似文献
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B. M. Whyman P. Johnson P. Mason H. Muirhead G. D. Patel G. W. van Apeldoorn D. Harting D. J. Holthuizen B. J. Pijlgroms M. M. H. M. Rijssenbeek 《Zeitschrift fur Physik C Particles and Fields》1982,12(3):203-216
We present results on inclusive baryon and meson resonance production in \(\bar pp\) interactions at 7.3 GeV/c. Total inclusive and semi-inclusive cross sections are given for Δ(1232),∑ *(1385), ?0,f andK *±(892) production. For the meson resonances separation into annihilation and non-annihilation components has been made, the annihilation component being dominant at this energy. We find that the energy dependence of inclusive cross sections for ?0 production inpp interactions and \(\bar pp\) non-annihilations shows a type of scaling behaviour previously reported for ?, ψ, ψ′ and ? production inpp interactions.Δ ++, ?0 andK *± production are studied in terms of Feynmanx,y * andp T 2 . For the vector mesons we compare they * andx dependences with the predictions of simple quark models. 相似文献
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在一系列H模放电条件下,建立了一个旨在研究等离子体温度分布剖面不变性的数据库。介绍了数据库建立过程中要解决的关键问题和所用软件,对等离子体温度分布剖面不变性及芯部约束与边缘参数的关系进行了研究。 相似文献
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