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991.
A theoretical study of the Cox-Symons model for normal muonium in Si is presented. The calculations are performed using polarized
basis set ab-initio Hartree Fock calculations followed by corrections for electron correlation. It is shown that, if lattice
relaxations are included, the antibonding site becomes a minimum of the potential energy surface (PES) for neutral interstitial
hydrogen. The energy at this minimum is lower than that at the undistorted tetrahedral interstitial site. The spin density
changes from being almost entirely on the muon (for Mu at the T site) to being almost entirely on a three-fold coordinated
Si atom (for Mu in the AB configuration). The mechanism required to explain the isotropy and magnitude of the observed hyperfine
tensor of Mu in c-Si is complicated. Large displacements of some host atoms are needed, and the system must be dynamic. However,
this model is the first able to produce a minimum of the PES together with an isotropic hyperfine interaction and a delocalized
spin density. 相似文献
992.
993.
At the critical point of the simple cubic Ising model, the radius of Coniglio-Klein clusters containings sites each is found by Monte Carlo simulation to be roughly 0.54s
0.4, consistent with the theoretically expected fractal dimension 2.5.Dedicated to Professor W. Brenig on the occasion of his 60th birthday 相似文献
994.
995.
Michael A. R. Meier Ulrich S. Schubert 《Journal of polymer science. Part A, Polymer chemistry》2003,41(19):2964-2973
Commercially available poly(vinyl chloride) (PVC) was covalently modified with terpyridine supramolecular binding units in a two‐step reaction. First, PVC was modified with aromatic thiols to introduce OH functionalities into the polymer backbone, which were subsequently reacted with an isocyanate‐functionalized terpyridine binding unit. The resulting functionalized material contained metal‐ion binding sites, which could be used for grafting and crosslinking reactions. A grafting experiment was performed with a small organic terpyridine ligand. The complexation of the modified PVC with several transition‐metal ions was studied with ultraviolet–visible spectroscopy and gel permeation chromatography. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2964–2973, 2003 相似文献
996.
Robert F. Dietrich Michael A. Marletta George L. Kenyon 《Magnetic resonance in chemistry : MRC》1980,13(2):79-88
Creatine (N-methyl-N-amidinoglycine), creatinine (1-methyl-2-aminoimidazolin-4-one) and a series of 38 of their close structural analogs have been examined using natural abundance 13C NMR spectroscopy at 25.16 MHz. Both proton-coupled and proton noise-decoupled spectra were recorded. Unequivocal assignments of the carbon resonances could be made in the vast majority of cases. Both 13C NMR chemical shifts and 1J(CH) values can be used to characterize and to differentiate readily between analogs of creatine and analogs of creatinine. For example, the 1J(CH) coupling constants for the α-carbons of the acyclic creatine analogs were all in the 140–142 Hz range, whereas the corresponding coupling constants for the related, cyclized creatinine analogs were all in the 150–152 Hz range. 相似文献
997.
998.
R.R. Meier 《Journal of Quantitative Spectroscopy & Radiative Transfer》1981,25(2):137-143
The consequences of angle-dependent partial frequency redistribution are investigated with a Monte Carlo model for a monochromatic source of radiation incident upon a uniform isothermal slab of resonantly-scattering atoms. The frequency redistribution probability is characterized by Hummer's RII function. Emergent line profiles are computed for optical depths of up to 105 at line-center. 相似文献
999.
Oxidation of cycloalkanone semicarbazones with lead tetraacetate leads to 2,5-dihydro-1,3,4-oxadiazol-2-ones, which under photolytic conditions eliminate nitrogen, carbon-monoxide and carbon dioxide. Cycloalkanones and azines are generated depending upon the solvent. 相似文献
1000.