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21.
Olson C Heth CL Lapidus SH Stephens PW Halder GJ Pokhodnya K 《The Journal of chemical physics》2011,135(2):024503
The M-[TCNE] (M = 3d metal; TCNE = tetracyanoethylene) system is one of the most interesting classes of molecule-based magnets, exhibiting a plethora of compositions and structures (inorganic polymer chains, 2D layers, 3D networks, and amorphous solids) with a wide range of magnetic ordering temperatures (up to 400 K). A systematic study of vibrational (both infrared and, for the first time, Raman) properties of the family of new TCNE-based magnets of M(II)(TCNE) (NCMe)(2)[SbF(6)] [M = Mn, Fe, Ni] composition is discussed in conjunction with their magnetic behavior and newly reso-lved crystal structures. The vibrational properties of the isolated TCNE(●-) anion in the paramagnetic Bu(4)N [TCNE(●-)] salt and recently characterized 2D layered magnet Fe(II)(TCNE)(NCMe)(2)[FeCl(4)] are also reported for comparison. Additionally, a linear correlation between ν(C=C) (a(g)) frequency of the TCNE ligand and its formal charge Z (the spin density on the π* orbital), Z = [1571 - ν(C=C) (a(g))]/154.5 [e], is presented. It is shown that monitoring Z by Raman spectroscopy is of great use in providing information that allows understanding the peculiarity of the superexchange interaction in M-[TCNE] magnets and establishing the structure-magnetic properties correlations in this class of magnetic material. 相似文献
22.
We give a brief history of degeneracy and cycling and discuss aspects of these topics that have been of interest to the author. 相似文献
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24.
Examples are given to show that the nonorientable genus of a graph is not additive over its blocks. A nonorientable analog for the Battle, Harary, Kodama, and Youngs Theorem is proved; this completely determines the nonorientable genus of a graph in terms of its blocks. It is also shown that one of the above counterexamples has the minimum possible order. 相似文献
25.
Saul Barshay 《Zeitschrift fur Physik C Particles and Fields》1980,4(1):63-66
The various symmetry breaking patterns that are possible with a 24-plet and a 5-plet of Higgs fields in SU(5) are classified. Spontaneous breakdown of SU(5) to SU(3)colour×U(1) em can be achieved (excluding the gauge hierarchy problem) without imposing unnatural constraints on the parameters of the Higgs potential. 相似文献
26.
We point out an unusual energy-independent component of the elementary two-body cross section for quark-antiquark annihilation into an intermediate vector boson in association with a jet which arises from a hypothetical spin-zero quantum. This leads to an unexpected extension of the transverse momentum distribution, with possible relevance to some of the novel events seen at the CERN SpS collider. 相似文献
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28.
Saul T. Epstein 《Chemical physics letters》1977,50(2):351-352
It is pointed out that an assumption common to all general discussions of the perturbation analysis of the variation method is sometimes unjustified, and some consequences are discussed. 相似文献
29.
We consider the problem of determining variational, external-field-dependent corrections to nonoptimal zero-field nonlinear parameters. Both a direct analytic perturbation analysis and finite perturbation methods are described in a general way and in detail for the SCF approximation. The abstract theory is illustrated by reference to the results of several explicit calculations. Also, the sensitivity of the results to the choice of zero-field values is discussed. 相似文献
30.
Saul T. Epstein 《International journal of quantum chemistry》1977,11(5):881-884
Some of Moccia's formulas (Int. J. Quant. Chem. 8 , 293 (1974)) for corrections to “not completely optimized variational parameters” are compared with those resulting from a perturbation theory analysis. It is not possible to choose the zero-order Hamiltonian (at least not in any simple way) so as to get exact agreement, but one choice does come close. 相似文献