731 research outputs found
Examination of the Jahn-Teller physics of NaNi02 and LiNi02 using x-ray absorption spectroscopy and configuration interaction
No full text This thesis examines available x-ray absorption spectroscopy (XAS) data for NiO, NaNi02 , and LiNi02 . The XAS examined is the Ni L-edge, 3d^n2p^6 →t 3d^(n+1)2p^5 . The experimental spectra are compared to spectra calculated using a configuration interaction approach. This approach reproduces the spectra accurately. The NaNi02 spectrum is shown to be sensitive to the Jahn-Teller distortion, while the LiNi02 spectrum is reproduced by a hybridized d^7-d^8 state that explains the lack of Jahn-Teller distortion in LiNi02 ThesisMaster of Science (MSc
Displacive Jahn--Teller transition in NaNiO
No full textBelow its Jahn--Teller transition temperature, , NaNiO has a monoclinic layered structure consisting of alternating layers of edge-sharing NaO and Jahn-Teller-distorted NiO octahedra. Above where NaNiO is rhombohedral, diffraction measurements show the absence of a cooperative Jahn-Teller distortion, accompanied by an increase in the unit cell volume. Using neutron total scattering, solid-state Nuclear Magnetic Resonance (NMR), and extended X-ray absorption fine structure (EXAFS) experiments as local probes of the structure we find direct evidence for a displacive, as opposed to order-disorder Jahn-Teller transition at . This is supported by \textit{ab initio} molecular dynamics (AIMD) simulations. To our knowledge this study is the first to show a displacive Jahn-Teller transition in any material using direct observations with local probe techniques.Under review. For SI, email the author
THE JAHN-TELLER EFFECT IN EXCITED STATES OF OCTAHEDRAL
No full textAuthor Institution: Department of Chemistry, Princeton UniversityWe have made a quantitative treatment of the Jahn-Teller effect in various excited states of in , a cubic crystal. The simplification of the experimental and theoretical work acheived by using this material gives us a chance to use the results as guides to the Jahn-Teller effect in other materials. The types of experiemtal work will be described and the estimates of the Jahn-Teller forces for various excited states will be discussed
EXPERIMENTAL MANIFESTATIONS OF THE JAHN-TELLER EFFECT
No full textAuthor Institution: JILA, University of ColoradoMolecules in orbitally degenerate states are subject to a number of effects that typical molecules are not. One such effect is Jahn-Teller coupling, which is the coupling between the vibrational and electronic angular momenta. This talk will review how Jahn-Teller coupling is manifested in the spectroscopy of molecules in degenerate electronic states. Both the vibronic and rovibronic structure of these states will be covered, with particular emphasis on the additional complications that occur when spin-orbit coupling is significant. The electronic spectra of the methoxy radicals (, and ) and of the Cp radical () will be used to illustrate how the Jahn-Teller effect can be observed experimentally. Lastly, it will be shown how recently developed ab initio methods can be used to aid in the interpretation of the experimental spectra of Jahn-Teller molecules
SPIN ORBIT COUPLING JAHN-TELLER (SOCJT)
No full textAuthor Institution: Corporate Strategic Research; ExxonMobil Research and Engineering, University of North Carolina; Dept. of Chemistry, The Ohio State UniversitySOCJT is a PC based program for determining the lowest energy eigenvalues of the Jahn-Teller Hamiltonian including linear and quadratic Jahn-Teller and spin-orbit terms. Calculations may be run for any molecule with non-cubic symmetry, having n arbitrary Jahn-Teller active modes, and arbitrary integer or half-integer spin state. In addition to calculating the lowest energy eigenvalues, SOCJT also computes several properties derived from the resulting eigenvectors, including the Coriolis coupling constants and the relative vibronic transition intensities to another electronic state. For the purpose of fitting experimental spectra, a non-linear least squares routine is included which allows for the fitting of the spin orbit coupling constant, , the n linear Jahn-Teller coupling constants , the n quadratic Jahn-Teller coupling constants , the n unperturbed harmonic vibrational frequencies, , and the n unperturbed anharmonic corrections , to experimentally determined line positions. SOCJT has been used successfully to fit the spectra of several Jahn-Teller active molecules, including , , , and
CAS-SCF COMPUTATIONS ON JAHN-TELLER, RENNER-TELLER AND SECOND ORDER JAHN-TELLER SYSTEMS
No full textAuthor Institution: Department of Chemistry, King's College London, StrandThe information that can be obtained ab initio CAS-SCF computations on Jahn-Teller, Renner-Teller and second order Jahn-Teller systems will be presented in order to stimulate discussion of how this information can be used to rationalize experimental data. Several examples will be presented for each potential surface topology. The Jahn-Teller crossing and associated minima and saddle points were optimised for the cyclopentadienyl radical at the CASSCF/cc-p VDZ level of theory. The structures were characterised by computing analytic force constants. Zero point energies calculated for all and isomers of the minima suggest an alternative interpretation of the experimentally observed degeneracy resolution. For the benzene radical cation, the Jahn-Teller topology has also been mapped out. Finally, the use of symmetry in characterising the second order John-Teller effect will also be discussed for pentalene and cyclooctatetraene
Newspaper serials in Tanzania: the case of Eric James Shigongo (with an interview)
No full textNewspaper serials have a long history in Tanzania. Since the privatisation of media in the 1990s, the number of newspapers and tabloids has multiplied, and serials have become abundant. I would dare to say that they are the most popular form of fiction at the moment in terms of quantity of readers. They are especially prevalent in the tabloids, where there often are more than three stories being serialised at a time. Some authors publish serials only occasionally, while there are also established serial writers such as Sultan Tamba, Faki A. Faki and Hamees M. Suba.However, the most prominent writer specialising in newspaper serials is Eric James Shigongo, who probably is also the most prolific author of popular literature of the last decade in Tanzania altogether. In his case, novel writing has reached a new quality as a well organised, apparently successful, self-owned business
THE EFFECTS OF SPIN-ORBIT COUPLING ON THE SPECTROSCOPY OF JAHN-TELLER ACTIVE MOLECULES
No full textAuthor Institution: Laser Spectroscopy Facility, Department of Chemistry, The Ohio State UniversityWe have developed a program that incorporates spin-orbit coupling directly into the normal Jahn-Teller Hamiltonian. The effects of spin-orbit coupling on the electronic spectroscopy of Jahn-Teller active molecules will be presented. The inclusion of spin-orbit coupling in the Hamiltonian is a necessity when both Jahn-Teller coupling and spin-orbit spin-orbit coupling are significant. Furthermore, the program handles an arbitrary number of Jahn-Teller active modes. We will show that for molecules that have more than one Jahn-Teller active mode, it is necessary to perform one multi-mode Jahn-teller calculation rather than several one-mode calculations. This combined theory has been applied to the electronic spectroscopy of the methoxy family of radicals and to the group IIA and IIB metalmonomethyl radicals. The relationship of {ab initio} calculations to the spin-orbit Jaha-Teller Hamiltonian will be discussed
The methodological status of co-authorship networks
No full textA powerful strategy within the study of collaboration
in science is to posit that co-authorship patterns
represent social networks.
It is prerequisite to an application of Social
Network Analysis (SNA) to define the network
entities. A network analysis of the inter-institutional
collaboration in COLLNET on the basis
of co-authorships was conducted. The study reveals
that it is crucial whether the co-authorship
itself is seen as an author's relational property or
as a social event that brings the authors together.
The former possibility is represented by a onemode
network in which each author can be related
to each other author. Quite distinct from
that are two-mode networks, the latter approach.
They consist of two single data sets in which relations
are only possible between different sets.
Different modes of representations require
different network approaches. One is that co-authorship
networks are seen as one-mode networks,
which has the advantage of the application
of a variety of measures. In contrast, twomode
networks, the other option, cannot be analysed
by standard techniques but its distinctive
features demand a new conceptualisation of
measures. In conclusion, the two-mode perspective
is more promising because it allows a dual
perspective on collaboration in science which includes
researchers as well as their scientific output
Orthogonality of Jahn-Teller axes in a dinuclear Cu(II) complex bridged by one F- anion
No full textThe dinuclear Cu(II) complex bridged by a single F- anion has orthogonal Jahn-Teller axes, which induce a ferromagnetic interaction between the intramolecular Cu(II) ions
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