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131.
Fuxing Pan Lukas Guggolz Florian Weigend Stefanie Dehnen 《Angewandte Chemie (International ed. in English)》2020,59(38):16638-16643
The Zintl anion (Ge2As2)2? represents an isostructural and isoelectronic binary counterpart of yellow arsenic, yet without being studied with the same intensity so far. Upon introducing [(PPh3)AuMe] into the 1,2‐diaminoethane (en) solution of (Ge2As2)2?, the heterometallic cluster anion [Au6(Ge3As)(Ge2As2)3]3? is obtained as its salt [K(crypt‐222)]3[Au6(Ge3As)(Ge2As2)3]?en?2 tol ( 1 ). The anion represents a rare example of a superpolyhedral Zintl cluster, and it comprises the largest number of Au atoms relative to main group (semi)metal atoms in such clusters. The overall supertetrahedral structure is based on a (non‐bonding) octahedron of six Au atoms that is face‐capped by four (GexAs4?x)x? (x=2, 3) units. The Au atoms bind to four main group atoms in a rectangular manner, and this way hold the four units together to form this unprecedented architecture. The presence of one (Ge3As)3? unit besides three (Ge2As2)2? units as a consequence of an exchange reaction in solution was verified by detailed quantum chemical (DFT) calculations, which ruled out all other compositions besides [Au6(Ge3As)(Ge2As2)3]3?. Reactions of the heavier homologues (Tt2Pn2)2? (Tt=Sn, Pb; Pn=Sb, Bi) did not yield clusters corresponding to that in 1 , but dimers of ternary nine‐vertex clusters, {[AuTt5Pn3]2}4? (in 2 – 4 ; Tt/Pn=Sn/Sb, Sn/Bi, Pb/Sb), since the underlying pseudo‐tetrahedral units comprising heavier atoms do not tend to undergo the said exchange reactions as readily as (Ge2As2)2?, according to the DFT calculations. 相似文献
132.
Kim Eklund Dr. Mikhail S. Kuklin Prof. Dr. Florian Kraus Prof. Antti J. Karttunen 《Chemphyschem》2020,21(8):802-808
Solid gold(I) fluoride remains as an unsynthesized and uncharacterized compound. We have performed a search for potential gold(I) fluoride crystal structures using USPEX evolutionary algorithm and dispersion-corrected hybrid density functional methods. Over 4000 AuF crystal structures have been investigated. Behavior of the AuF crystal structures under pressure was studied up to 25 GPa, and we also evaluated the thermodynamic stability of the hypothetical AuF crystal structures with respect to AuF3, AuF5, and Au3F8. Mixed-valence compound Au3[AuF4] with Au atoms in various formal oxidation states emerged as the thermodynamically most stable AuF species. 相似文献
133.
Dr. Dominique Laniel Dr. Florian Trybel Dr. Adrien Néri Yuqing Yin Andrey Aslandukov Dr. Timofey Fedotenko Saiana Khandarkhaeva Dr. Ferenc Tasnádi Dr. Stella Chariton Dr. Carlotta Giacobbe Dr. Eleanor Lawrence Bright Dr. Michael Hanfland Dr. Vitali Prakapenka Prof. Dr. Wolfgang Schnick Prof. Dr. Igor A. Abrikosov Prof. Dr. Leonid Dubrovinsky Prof. Dr. Natalia Dubrovinskaia 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(62):e202201998
Non-metal nitrides are an exciting field of chemistry, featuring a significant number of compounds that can possess outstanding material properties. These properties mainly rely on maximizing the number of strong covalent bonds, with crosslinked XN6 octahedra frameworks being particularly attractive. In this study, the phosphorus–nitrogen system was studied up to 137 GPa in laser-heated diamond anvil cells, and three previously unobserved phases were synthesized and characterized by single-crystal X-ray diffraction, Raman spectroscopy measurements and density functional theory calculations. δ-P3N5 and PN2 were found to form at 72 and 134 GPa, respectively, and both feature dense 3D networks of the so far elusive PN6 units. The two compounds are ultra-incompressible, having a bulk modulus of K0=322 GPa for δ-P3N5 and 339 GPa for PN2. Upon decompression below 7 GPa, δ-P3N5 undergoes a transformation into a novel α′-P3N5 solid, stable at ambient conditions, that has a unique structure type based on PN4 tetrahedra. The formation of α′-P3N5 underlines that a phase space otherwise inaccessible can be explored through materials formed under high pressure. 相似文献
134.
We present a higher-order cut cell immersed boundary method (IBM) for the simulation of high Mach number flows. As a novelty on a cut cell grid, we evaluate an adaptive local time stepping (LTS) scheme in combination with an artificial viscosity–based shock-capturing approach. The cut cell grid is optimized by a nonintrusive cell agglomeration strategy in order to avoid problems with small or ill-shaped cut cells. Our approach is based on a discontinuous Galerkin discretization of the compressible Euler equations, where the immersed boundary is implicitly defined by the zero isocontour of a level set function. In flow configurations with high Mach numbers, a numerical shock-capturing mechanism is crucial in order to prevent unphysical oscillations of the polynomial approximation in the vicinity of shocks. We achieve this by means of a viscous smoothing where the artificial viscosity follows from a modal decay sensor that has been adapted to the IBM. The problem of the severe time step restriction caused by the additional second-order diffusive term and small nonagglomerated cut cells is addressed by using an adaptive LTS algorithm. The robustness, stability, and accuracy of our approach are verified for several common test cases. Moreover, the results show that our approach lowers the computational costs drastically, especially for unsteady IBM problems with complex geometries. 相似文献
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139.
Dr. David Martin Dr. Nicolas Lassauque Florian Steinmann Gerald Manuel Prof. Guy Bertrand 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(44):14895-14901
Experimental and computational investigations of anti‐Bredt amidinium salts are presented. Calculations show that the pyramidalization of an amino group can significantly destabilize the formal carbocation center of amidiniums, due to the decreased π donation. In some cases, the unfavorable ‐I effect of nitrogen surpasses its beneficial +M effect, and amidiniums become less stable than iminiums. It is shown that although 1‐aza‐3‐azonia[3.3.1]bicyclo‐non‐2‐enes can be isolated, they feature a nonclassical reactivity, which is more typical for iminium than amidinium salts, such as pronounced electrophilicity and azomethineylide instead of carbene formation. 相似文献