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FENGHUANG diffractometer at CMRR is a neutron diffractometer dedicated for high pressure experiments. After updating the neutron guide and monochromator, now the neutron flux at the sample position can get increased up to 2.84x106 ns--1⋅cm-2. Based on the FENGHUANG diffractometer, comprehensive high pressure devices and techniques have been developed, such as gas cells, piston cylinders cell, clamp cell, PE press (VX4), opposite anvil press (HP3-1500) along with sample heating and cooling system, and the alignment system for high pressure devices. Moreover, with the modified high pressure and high temperature cell assemblies, the pressure can be up to 34 GPa while the temperature reaches 1 500 °C at maximum in the angle-dispersive neutron diffraction. Recently, some scientific research have been performed, like the solubility of NaCl at high pressure, the intergranular strain evolution of HMX, and the pressure-induced polymerization. All these experimental experiences from FENGHUANG diffractometer could not only help to promote the development of high pressure techniques on neutron scattering facilities, but also contribute to the users for their high pressure studies. [ABSTRACT FROM AUTHOR]

Pressure‐induced polymerization (PIP) of aromatics is a novel method for constructing sp3‐carbon frameworks, and nanothreads with diamond‐like structures were synthesized by compressing benzene and its derivatives. Here by compressing a benzene‐hexafluorobenzene cocrystal (CHCF), H‐F‐substituted graphane with a layered structure in the PIP product was identified. Based on the crystal structure determined from the in situ neutron diffraction and the intermediate products identified by gas chromatography‐mass spectrum, we found that at 20 GPa CHCF forms tilted columns with benzene and hexafluorobenzene stacked alternatively, and leads to a [4+2] polymer, which then transforms to short‐range ordered H‐F‐substituted graphane. The reaction process involves [4+2] Diels–Alder, retro‐Diels–Alder, and 1‐1′ coupling reactions, and the former is the key reaction in the PIP. These studies confirm the elemental reactions of PIP of CHCF for the first time, and provide insight into the PIP of aromatics. Short‐range ordered H,F‐substituted graphane was obtained by compressing benzene and hexafluorobenzene cocrystals. By using neutron diffraction and GC‐MS, the reaction process and elementary reactions were identified. The reaction process involves [4+2]Diels–Alder, retro‐Diels–Alder, and 1‐1′ coupling reactions, and the Diels–Alder reaction is the key reaction in the polymerization process. [ABSTRACT FROM AUTHOR]

The newly developed full-potential linearized augmented plane wave (LAPW) and local orbitals (lo) based on standard APW methods are briefly introduced, and the structure and magnetic properties of R(Fe, Si)12 compounds ( R = Y, Nd) are calculated using the method. The distribution of Si at different sites is analyzed based on total energy of one crystal unit with structure having been optimized. The characters of magnetic moments, total density of states (TDOS) and partial density of states (PDOS) for different crystal sites Si occupies are obtained and analyzed. The results show that the total magnetic moments of RFe10Si2 ( R = Y, Nd) are larger than those of RFe10 M2 ( M = Ti, V, Cr, Mn, Mo and W) and the hybridization mechanism is seen as follows. Si(8j) reduce the magnetic moments of Fe at three sites, however, Si(8f) mainly reduce the magnetic moments of Fe(8i) and Fe(8j) atoms. The Curie temperature is markedly enhanced by the introduction of Si atoms according to spin fluctuation of DOS at Fermi level. [ABSTRACT FROM AUTHOR]

Pressure-induced polymerization (PIP) of aromatics is a novel method for constructing sp 3 -carbon frameworks, and nanothreads with diamond-like structures were synthesized by compressing benzene and its derivatives. Here by compressing a benzene-hexafluorobenzene cocrystal (CHCF), H-F-substituted graphane with a layered structure in the PIP product was identified. Based on the crystal structure determined from the in situ neutron diffraction and the intermediate products identified by gas chromatography-mass spectrum, we found that at 20 GPa CHCF forms tilted columns with benzene and hexafluorobenzene stacked alternatively, and leads to a [4+2] polymer, which then transforms to short-range ordered H-F-substituted graphane. The reaction process involves [4+2] Diels-Alder, retro-Diels-Alder, and 1-1' coupling reactions, and the former is the key reaction in the PIP. These studies confirm the elemental reactions of PIP of CHCF for the first time, and provide insight into the PIP of aromatics., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)