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81.
Single crystal X-ray diffraction measurements on MxMo3S4 compounds (M = Cu, Ag, Sn, In) yield evidence for the existence of a charge transfer from the interstitial element M to the Mo6S8 building blocks. The importance of this transfer was estimated from the contraction of the Mo6 octahedron as a function of the valency and the concentration of the cations. It is suggested that this effect stabilises the structure and has a strong influence on the superconducting transition temperature. Bonding is discussed using a simple valence bond model which is based on the electron requirement of the Mo6 octahedron to form 12 covalent bonds. 相似文献
82.
J.-J. Didisheim K. Yvon D. Shaltiel P. Fischer P. Bujard E. Walker 《Solid State Communications》1979,32(11):1087-1090
A neutron diffraction analysis at room temperature of ZrV2D4·5 has been made. The deuterium atoms are found to occupy two types of tetrahedral interstices in the metal atom host structure. One is formed by 1 Zr and 3 V atoms and has an occupancy of 39%, whereas the other one is formed by 2 Zr and 2 V atoms, having an occupancy of 25%. Together these interstices can be considered as forming a three-dimensional infinite network of diffusion paths which is similar to that observed in the deuterated hexagonal Laves-phase ZrMn2D3. The adjacent D atom sites in this network are about 1.3 åA apart and the average Zr-D and V-D distances are 2.10 and 1.77 åA, respectively. 相似文献
83.
84.
Joseph R. Royer Yvon J. Gay Joseph M. Desimone Saad A. Khan 《Journal of Polymer Science.Polymer Physics》2000,38(23):3168-3180
A high‐pressure extrusion slit die rheometer was constructed to measure the viscosity of polymer melts plasticized by liquid and supercritical CO2. A novel gas injection system was devised to accurately meter the follow of CO2 into the extruder barrel. Measurements of pressure drop, within the die, confirm the presence of a one‐phase mixture and a fully developed flow during viscosity measurements. Experimental measurements of viscosity as a function of shear rate, pressure, temperature, and CO2 concentration were conducted for three commercial polystyrene melts. The CO2 was shown to be an effective plasticizer for polystyrene, lowering the viscosity of the polymer melt by as much as 80%, depending of the process conditions and CO2 concentration. Existing theories for viscoelastic scaling of polymer melts and the prediction of Tg depression by a diluent were used to develop a free volume model for predicting the effects of CO2 concentration and pressure on polymer melt rheology. The free volume model, dependent only on material parameters of the polymer melt and pure CO2, was shown to accurately collapse the experimental data onto a single master curve independent of pressure and CO2 concentration for each of the three polystyrene samples. This model constitutes a simple predictive set of equations to quantify the effects of gas‐induced plasticization on molten polymer systems. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 3168–3180, 2000 相似文献
85.
Vincenzo Barone Gabriella Capecchi Yvon Brunel Marie-Louise Dheu Andris Robert Subra 《Journal of computational chemistry》1997,18(14):1720-1728
Parameters suitable for extending the AMBER force field for nucleic acids and proteins to open-shell derivatives of amino acid residues are proposed and tested. Two new atom types (radical carbon [CE] and hydrogen directly bonded to it [HE]) are introduced, whose parameters have been determined by a best fitting of quantum-mechanical computations of the simplest analogue of glycine radical (GlyR) in a peptide. The new force field is able to fit the reference results concerning both the structural parameters and the relative stabilities of the different conformers. It has been next applied to a conformational study of the distortions induced by extraction of the glycine Hα atom in an initially helical structure of a dodecamer of alanine including a central glycine residue. Our results show that the helical structure corresponds to a local energy minimum, but deeper minima are found which correspond to a fully planar GlyR residue included in a distorted helical sequence. © 1997 John Wiley & Sons, Inc. J Comput Chem 18 : 1720–1728, 1997 相似文献
86.
P K Datta C Yau T S Hooper B L Yvon J L Charlton 《The Journal of organic chemistry》2001,66(25):8606-8611
Acid-catalyzed cyclizations of E,E-dibenzylidenesuccinate esters have been developed as an efficient synthetic route to 1-aryl-1,2-dihydronaphthalenes. This reaction has been used in the synthesis of the naturally occurring lignans (+/-)-cagayanin and (+/-)-galbulin. 相似文献
87.
Benjamin Stamm Louis Lagardère Giovanni Scalmani Paolo Gatto Eric Cancès Jean-Philip Piquemal Yvon Maday Benedetta Mennucci Filippo Lipparini 《International journal of quantum chemistry》2019,119(1):e25669
We illustrate the domain decomposition Conductor-like Screening Model (ddCOSMO) implementation and how to couple it with an existing classical or quantum mechanical (QM) code. We review in detail what input needs to be provided to ddCOSMO and how to assemble it, describe how the ddCOSMO equations are solved and how to process the results to assemble the required quantities, such as Fock matrix contributions for the QM case, or forces for the classical one. Throughout the article, we will make explicit references to the ddCOSMO module, which is an open source, Fortran 90 implementation of ddCOSMO that can be downloaded and distributed under the LGPL license. 相似文献
88.
Boulay A Artigau M Coulais Y Picard C Mestre-Voegtlé B Benoist E 《Dalton transactions (Cambridge, England : 2003)》2011,40(23):6206-6209
In this communication, a novel synthetic pathway has been applied to prepare a dual imaging agent in a single molecule. The dinuclear Re(I)/Tc(I) complex 6, namely [Re(CO)(3)(bipy){(4-PyrIDA)Tc(CO)(3)}], is the first example of a Re/Tc-based heterometallic assembly which could act as a potential bimodal Optical/SPECT probe. Interestingly, the Re(I) complex intermediate 4 exhibits significant photophysical properties for biological applications. 相似文献
89.
Yvon MADAY 《数学年刊B辑(英文版)》2014,35(1):1-24
The (continuous) finite element approximations of different orders for the computation of the solution to electronic structures were proposed in some papers and the performance of these approaches is becoming appreciable and is now well understood. In this publication, the author proposes to extend this discretization for full-potential electronic structure calculations by combining the refinement of the finite element mesh, where the solution is most singular with the increase of the degree of the polynomial approximations in the regions where the solution is mostly regular. This combination of increase of approximation properties, done in an a priori or a posteriori manner, is well-known to generally produce an optimal exponential type convergence rate with respect to the number of degrees of freedom even when the solution is singular. The analysis performed here sustains this property in the case of Hartree-Fock and Kohn-Sham problems. 相似文献
90.
We have proposed in a previous note a time discretization for partial differential evolution equation that allows for parallel implementations. This scheme is here reinterpreted as a preconditioning procedure on an algebraic setting of the time discretization. This allows for extending the parallel methodology to the problem of optimal control for partial differential equations. We report a first numerical implementation that reveals a large interest. To cite this article: Y. Maday, G. Turinici, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 387–392. 相似文献