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71.
Linda Fluyt Kris Driesen Christiane Görller-Walrand 《Journal of solid state chemistry》2005,178(2):429-434
A new approach to unravel the site symmetry of lanthanides in solutions is presented. The magnetic circular dichroism spectra of Eu3+ in the symmetries D3h, C4v and D2d are simulated. In these simulations, the main idea is to introduce the magnetic field along a 3-fold axis, being the resultant of the three equivalent X-, Y- and Z-direction of a cube. This implies that the parallel and perpendicular Zeeman effects are taken into account simultaneously. 相似文献
72.
Binary zirconium orthophosphates R1/3Zr2(PO4)3 and M1/4Zr2(PO4)3, where R = Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu; M = Th, U, have been synthesized and studied by IR spectroscopy [structural family of NaZr2(PO4)3 (NZP)]. Vibrational analysis for the PO4 tetrahedron and investigation of symmetry relations among trigonal NZP phases showed that ordering of lanthanide atoms in structures of NaZr2(PO4)3 type with space group R
c leads to symmetry reduced to P
c. The lanthanide atoms occupy the 2b sites. The phosphorus atoms occupy two independent sites: 6f with C
2 symmetry and 12g with C
1 symmetry. Factor group analysis admits that the IR spectrum can contain eight v3 bands and two v1 bands of the stretching vibrations of the PO4 ions. The M atoms of actinides occupy statistical positions in the structure, and space group R
c is retained.Original Russian Text Copyright © 2004 by V. S. Kurazhkovskaya, D. M. Bykov, and A. I. Orlova__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 1013–1019, November–December, 2004. 相似文献
73.
John Ross George M. Whitesides Horia Metiu 《Angewandte Chemie (International ed. in English)》1979,18(5):377-392
The influence of molecular symmetry on reaction rates is examined with an approach in which reactions are viewed as electronic transitions between states of reacants and products (described, in turn by quasiadiabatic potential surface). The moleculer Hamiltonian is used to derive selection rules for these transitions. The complete Hamilatonian has no useful symmetery. Neglect of non-Born-Oppenheimer and spin-orbit terms (and of other angular momentum coupling terms) leads to an apporixmate Hamiltonian and to selection rules which from the basis of the Woodward-Hoffmann rules. This apporch provides an alternative to the adiabatic potantial surfaces, reaction coordinates, and transition state theory used in more familiar discussions of the Woodward-Hoffmann rules. Further, it provides a particulary clear method for discussing violations of these symmetry rules, and for differentiating concerted and nonconcerted reactions. 相似文献
74.
75.
A closed‐form expression has been derived to obtain the N‐dimensional rectangular atomic wave functions. The wave functions can be obtained straightforwardly with the knowledge of the angular momentum quantum numbers and the dimension and there is no need to employ recursive methods as in previous works. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem 88: 263–274, 2002 相似文献
76.
Roberto Acevedo Teodoro Meruane Jorge R. Letelier 《Theoretical chemistry accounts》1984,64(5):339-369
The theory of radiative transitions, in centrosymmetric complexes, is examined in great detail, within the framework of the crystal field method.In connection with radiative transitions, the current method of calculations, with and without invoking closure approximation, are considered from a purely theoretical point of view, by taking advantage of the irreducible tensor method put forward by Griffith.Explicit equations are derived throughout the course of this work to account for the vibronic electric dipole moments, associated with d-d and f-f type of excitations.At high Academy of Pedagogic Sciences, Santiago, Chile. 相似文献
77.
78.
Tidjani Ngadi 《International journal of quantum chemistry》2003,94(2):65-74
In this article, we make a connection between the Rumer transformation, used in the study of the genetic code‐doublets, and the negation of classic logic. A unified classification is given, relying on two Klein's 4‐groups describing the symmetries of the 16 doublets of nitrogenous bases and those of the 16 binary connectives of classic logic, both groups being subgroups of a larger noncommutative group with eight elements we identify as the dihedral group D4. Also, some connections with other works are briefly considered. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003 相似文献
79.
80.
R.V. Denys V.A. Yartys Masashi Sato R.G. Delaplane 《Journal of solid state chemistry》2007,180(9):2566-2576
A new intermetallic deuteride Ce2Ni7D4.7 with an anomalous volume expansion has been studied. Its structure was solved on the basis of in situ neutron diffraction data. Expansion proceeds along the c-axis and within the CeNi2 slabs only. All D atoms are located inside these slabs and on the border between CeNi2 and CeNi5. Ordering of D atoms in the bulk of CeNi2 is accompanied by substantial deformation of these slabs thus lowering the hexagonal symmetry to orthorhombic [space group Pmcn (No. 62); a=4.9251(3) Å, b=8.4933(4) Å, c=29.773(1) Å]. Inside the CeNi2 layer the hydrogen sublattice is completely ordered; all D-D distances exceed 2.0 Å. Local coordination of Ni by D inside the CeNi2 blocks is of “open”, saddle-like type. Hydrogen ordering is mainly determined by Ce-H and H-H interactions. The pressure-composition-temperature measurements yielded the following thermodynamic parameters of the formation of the hydride: ΔH=−22.4 kJ/molH, ΔS=−59.9 J/(K molH). 相似文献