排序方式: 共有15条查询结果,搜索用时 15 毫秒
1.
J.C.S. Rocha B.V. Costa P.Z. Coura S.A. Leonel R.A. Dias 《Journal of magnetism and magnetic materials》2012
In this work we report a numerical Monte Carlo study of the behavior of a magnetic nano-disk put over an antiferromagnetic substrate. Three approaches were considered for describe the substrate: (1) A stacked antiferromagnetic configuration, (2) an Ising like arrangement and (3) Heisenberg like spins. For the Heisenberg case we still have considered an easy-plane and an easy-axis symmetry of the substrate. The hysteresis loop for the nano-disk is obtained by considering the three cases. The signature of the vortex in the nano-disk appears as small jumps in the hysteresis curve. Exchange bias effects are observed since the substrate has an easy axis symmetry. 相似文献
2.
Dr. Thomas G. Hayhow Rachel E. A. Borrows Dr. Coura R. Diène Gary Fairley Dr. Charlene Fallan Dr. Shaun M. Fillery Dr. James S. Scott Dr. David W. Watson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(70):16818-16823
A palladium-catalysed Buchwald–Hartwig amination for lenalidomide-derived aryl bromides was optimised using high throughput experimentation (HTE). The substrate scope of the optimised conditions was evaluated for a range of alkyl- and aryl- amines and functionalised aryl bromides. The methodology allows access to new cereblon-based bifunctional proteolysis targeting chimeras with a reduced step count and improved yields. 相似文献
3.
Mohallem JR Coura Tde O Diniz LG de Castro G Assafrão D Heine T 《The journal of physical chemistry. A》2008,112(38):8896-8901
The adiabatic finite-nuclear-mass-correction (FNMC) to the electronic energies and wave functions of atoms and molecules is formulated for density-functional theory and implemented in the deMon code. The approach is tested for a series of local and gradient corrected density functionals, using MP2 results and diagonal-Born-Oppenheimer corrections from the literature for comparison. In the evaluation of absolute energy corrections of nonorganic molecules the LDA PZ81 functional works surprisingly better than the others. For organic molecules the GGA BLYP functional has the best performance. FNMC with GGA functionals, mainly BLYP, show a good performance in the evaluation of relative corrections, except for nonorganic molecules containing H atoms. The PW86 functional stands out with the best evaluation of the barrier of linearity of H2O and the isotopic dipole moment of HDO. In general, DFT functionals display an accuracy superior than the common belief and because the corrections are based on a change of the electronic kinetic energy they are here ranked in a new appropriate way. The approach is applied to obtain the adiabatic correction for full atomization of alcanes C(n)H(2n+2), n = 4-10. The barrier of 1 mHartree is approached for adiabatic corrections, justifying its insertion into DFT. 相似文献
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We use Monte Carlo to investigate the Berezinskii–Kosterlitz–Thouless transition close to the site percolation threshold in a square lattice. Several thermodynamic quantities are calculated for lattice sizes L×L, from 16<L<640. Our results are consistent with an infinite order transition for any value of the concentration of magnetic sites. We found that close to the critical percolation concentration, pc (0.592746), the Berezinskii–Kosterlitz–Thouless transition temperature goes to zero as TBKT∝(p−pc)0.908 and the specific heat behaves as Tsh∝p1.133. 相似文献
6.
Lemaire S Houpis IN Xiao T Li J Digard E Gozlan C Liu R Gavryushin A Diène C Wang Y Farina V Knochel P 《Organic letters》2012,14(6):1480-1483
A general, transition-metal-free, highly stereoselective cross-coupling reaction between glycosyl bromides and various arylzinc reagents leading to β-arylated glycosides is reported. The stereoselectivity of the reaction is explained by invoking anchimeric assistance via a bicyclic intermediate. Stereochemical probes confirm the participation of the 2-pivaloyloxy group. Finally, this new method was applied to a short and efficient stereoselective synthesis of Dapagliflozin and Canagliflozin. 相似文献
7.
F. Sato A.S. Moreira P.Z. Coura S.O. Dantas S.B. Legoas D. Ugarte D.S. Galvão 《Applied Physics A: Materials Science & Processing》2005,81(8):1527-1531
Metallic nanowires (NWs) have been the object of intense theoretical and experimental investigations in the last years. In
this work we present and review a new methodology we developed to study NW formation from mechanical stretching. This methodology
is based on tight-binding molecular dynamics techniques using second-moment approximations. This methodology had been proven
to be very effective in the study of NWs, reliably reproducing the main experimentally observed structural features. We have
also investigated the problem of determining from what regions the atoms composing the linear atomic chains come. Our results
show that ∼90% of these atoms come from outmost external layers.
Electronic supplementary material Supplementary material is available in the online version of this article at
and is accessible for authorized users.
PACS 66.30.Pa; 68.65.-k; 68.03.Hj 相似文献
8.
Legoas SB Coluci VR Braga SF Coura PZ Dantas SO Galvão DS 《Physical review letters》2003,90(5):055504
Recently, Zheng and Jiang [Phys. Rev. Lett. 88, 045503 (2002)]] have proposed that multiwalled carbon nanotubes could be the basis for a new generation of nano-oscillators in the several gigahertz range. In this Letter, we present the first molecular dynamics simulation for these systems. Different nanotube types were considered in order to verify the reliability of such devices as gigahertz oscillators. Our results show that these nano-oscillators are dynamically stable when the radii difference values between inner and outer tubes are of approximately 3.4 A. Frequencies as large as 38 GHz were observed, and the calculated force values are in good agreement with recent experimental investigations. 相似文献
9.
J.H. Silva D. Toscano F. Sato P.Z. Coura B.V. Costa S.A. Leonel 《Journal of magnetism and magnetic materials》2012
In this work we have used spin dynamics simulations to study the gyrotropic frequency behavior in nano-disks of Permalloy with magnetic impurities. We consider the effect of attractive impurity and repulsive impurity placed near the vortex core gyrotropic trajectory. We observed that the gyrotropic frequency is affected by the presence of impurity. The gyrotropic frequency shift depends on the relative position between the impurity and the vortex core gyrotropic trajectory and if impurity is attractive or repulsive. Our results agree with the analytical model and with experimental behavior for the gyrotropic frequency shown in the literature. 相似文献
10.
Isoxazole‐Embedded Allylic Zinc Reagent for the Diastereoselective Preparation of Highly Functionalized Aldol‐Type Derivatives Bearing a Stereocontrolled Quaternary Center 下载免费PDF全文
Lydia Klier Coura R. Diène Manuel Schickinger Albrecht Metzger Andreas J. Wagner Prof. Dr. Konstantin Karaghiosoff Prof. Dr. Ilan Marek Prof. Dr. Paul Knochel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(43):14096-14101
Highly functionalized aldol‐type products bearing a β‐quaternary center and a stereoselectively controlled γ‐hydroxy function are readily prepared by the diastereoselective addition of an allylic zinc reagent embedded in an isoxazole ring to various aromatic and heteroaromatic aldehydes, in the presence of Lewis acids, such as MgCl2 or LaCl3?2 LiCl. After reductive cleavage of the N?O bond by using Fe, NH4Cl, aldol‐type products bearing a stereocontrolled β‐quaternary center and a γ‐hydroxy group were observed. The benzylic reactivity of the isoxazolylmethylzinc reagent towards other electrophiles, such as acid chlorides, aryl and allylic halides, as well as aldehydes in the presence of BF3?OEt2 are also described. 相似文献