نتایج جستجو برای: tetrahedral arrangement
تعداد نتایج: 41000 فیلتر نتایج به سال:
Layered materials with intercalated ions exhibit a variety of intriguing physical and chemical properties. To obtain the exotic two-dimensional (2D) materials, doping alteration crystals by ionic guest species are widely used in science. However, ion-intercalated layered properties induced change interlayered structures rarely studied. Hence, we demonstrate emergence superconductivity new struc...
this research work is devoted to the development of a mathematical model for the simulation of the flow of polymeric melts through the die region of extruders. a set of governing equations are solved using finite element method. standard galerkin technique is used in conjunction with the mixed scheme to solve the flow equation. due to the non-linear nature of global equations, the picard iterat...
High energy x-ray diffraction measurements of pure amorphous Ge were made and its radial distribution function (RDF) was determined at high resolution, revealing new information on the atomic structure of amorphous semiconductors. Fine structure in the second peak in the RDF provides evidence that a fraction of third neighbors are closer than some second neighbors; taking this into account lead...
The atomic-structure characterization of alloy nanoclusters (NCs) remains challenging but is crucial in order to understand the synergism and develop new applications based upon the distinct properties of alloy NCs. Herein, we report the synthesis and X-ray crystal structure of the Pt1Ag28(S-Adm)18(PPh3)4 nanocluster with a tetrahedral shape. Pt1Ag28 was synthesized by reacting Pt1Ag24(SPhMe2)1...
Silicon-29 magic-angle-spinning NMR spectroscopy has been used to investigate the silicon-aluminum distribution in natural samples of analcite and leucite (before and after heat treatment) as well as a leucite synthesized from a gel. Three different simulation programs have been developed to fit the experimental spectra. For two we assume a different aluminum occupancy fraction g~ for each of t...
The atomic-structure characterization of alloy nanoclusters (NCs) remains challenging but is crucial in order to understand the synergism and develop new applications based upon the distinct properties of alloy NCs. Herein, we report the synthesis and X-ray crystal structure of the Pt1Ag28(S-Adm)18(PPh3)4 nanocluster with a tetrahedral shape. Pt1Ag28 was synthesized by reacting Pt1Ag24(SPhMe2)1...
Using first-principles methods, we predict the energy landscape and ferroelectric states of double perovskites of the form AA′BB′O6 in which the atoms on both the A and B sites are arranged in rocksalt order. While we are not aware of compounds that occur naturally in this structure, they might be realizable by directed synthesis, as has recently been demonstrated experimentally. The high-symme...
For several decades attention has been directed to natural polysaccharide gels and synthesized polymer gels. The structure-function relationships at molecular level in water of polysaccharides, κ-carrageenan, ι-carrageenan, agarose (agar), and gellan family of polysaccharides (gellan, welan, rhamsan, S-657, deacetylated rhamsan and native gellan gum), which are industrially useful polysaccharid...
New multinary selenides Ae3SnPn2Se8 (Ae = Sr, Ba; Pn = Sb, Bi), Sr8.01Ge2.04Bi7.95Se24, and Sr8YGe2Bi7Se24 were synthesized by solid-state reaction, and their structures were determined by single-crystal X-ray diffraction. These compounds crystallize in orthorhombic space group Pnma (no. 62) for Ae3SnPn2Se8 (Ae = Sr, Ba; Pn = Sb, Bi) and in Pna21 (no. 33) for Sr8.01Ge2.04Bi7.95Se24 and Sr8YGe2B...
Pseudo-octahedral M(II) 6 L4 capsules result from the subcomponent self-assembly of 2-formylphenanthroline, threefold-symmetric triamines, and octahedral metal ions. Whereas neutral tetrahedral guests and most of the anions investigated were observed to bind within the central cavity, tetraphenylborate anions bound on the outside, with one phenyl ring pointing into the cavity. This binding conf...
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