129,388 research outputs found
Rearrangements and Tunneling Splittings in Small Water Clusters
Recent far-infrared vibration-rotation tunneling (FIR-VRT) experiments pose
new challenges to theory because the interpretation and prediction of such
spectra requires a detailed understanding of the potential energy surface (PES)
away from minima. In particular we need a global description of the PES in
terms of a complete reaction graph. Hence all the transition states and
associated mechanisms which might give rise to observable tunneling splittings
must be characterized. It may be possible to guess the detailed permutations of
atoms from the transition state alone, but experience suggests this is unwise.
In this contribution a brief overview of the issues involved in treating the
large amplitude motions of such systems will be given, with references to more
detailed discussions and some specific examples. In particular we will consider
the effective molecular symmetry group, the classification of rearrangement
mechanisms, the location of minima and transition states and the calculation of
reaction pathways. The application of these theories to small water clusters
ranging from water dimer to water hexamer will then be considered. More details
can be found in recent reviews.Comment: 15 pages, 5 figures. This paper was prepared in August 1997 for the
proceedings volume of the NATO-ASI meeting on "Recent Theoretical and
Experimental Advances in Hydrogen Bonded Clusters" edited by Sotiris
Xantheas, which has so far not appeare
A summary of terminology used in tephra-related studies
The word ‘tephra’, derived from a Greek word for ash, is a collective term for all the unconsolidated, primary pyroclastic products of a volcanic eruption. We summarise here the meanings and applicability of this and related terms, including tephrostratigraphy, tephrochronology, tephrochronometry, tephrology, and cryptotephra. These and other tephra-based terms, some of which are erroneous or unnecessary, have been used in a wide range of stratigraphic and paleoenvironmental disciplines and in archaeology
Foreword and Prologue
Milton Konvitz (Ph.D. \u2733) embodied the spirit of Cornell University. An authority on civil rights and human rights, and constitutional and labor law, he served on the Cornell faculty for 27 years, holding dual appointments at the Law School and the School of Industrial and Labor Relations. This section includes the foreword by Robert B. McKersie and the prologue in four chapters: (1) The Making of a Scholar; (2) Civil Rights; (3) Fundamental Liberties; and (4) Judaic and American Ideals
Theory of PbTiO3, BaTiO3, and SrTiO3 Surfaces
First-principles total-energy calculations are carried out for (001) surfaces
of the cubic perovskite ATiO3 compounds PbTiO3, BaTiO3, and SrTiO3. Both
AO-terminated and TiO2-terminated surfaces are considered, and fully-relaxed
atomic configurations are determined. In general, BaTiO3 and SrTiO3 are found
to have a rather similar behavior, while PbTiO3 is different in many respects
because of the partially covalent character of the Pb-O bonds. PbTiO3 and
BaTiO3 are ferroelectrics, and the influence of the surface upon the
ferroelectric distortions is studied for the case of a tetragonal ferroelectric
distortion parallel to the surface. The surface relaxation energies are found
to be substantial, i.e., many times larger than the bulk ferroelectric well
depth. Nevertheless, the influence of the surface upon the ferroelectric order
parameter is modest, and is qualitatively as well as quantitatively different
for the two materials. Surface energies and electronic properties are also
computed. It is found that for BaTiO3 and SrTiO3 surfaces, both AO-terminated
and TiO2-terminated surfaces can be thermodynamically stable, whereas for
PbTiO3 only the PbO surface termination is stable.Comment: 13 pages with 3 postscript figures embedded. Uses REVTEX and epsf
macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/index.html#bm_pbsur
A New Expansion for Nucleon-Nucleon Interactions
We introduce a new and well defined power counting for the effective field
theory describing nucleon-nucleon interactions. Because of the large NN
scattering lengths it differs from other applications of chiral perturbation
theory and is facilitated by introducing an unusual subtraction scheme and
renormalization group analysis. Calculation to subleading order in the
expansion can be done analytically, and we present the results for both the 1S0
and 3S1-3D1 channels.Comment: 10 pages, 3 figures, latex. Corrected typo, small change to tex
Learning by building digital libraries
The implications of using digital library software in educational contexts, for both students and software developers, are discussed using two case studies of students building digital libraries
Intraday credit: risk, value, and pricing
An abstract for this article is not availableElectronic funds transfers ; Payment systems ; Overdrafts
Kinetic Monte Carlo simulations of oscillatory shape evolution for electromigration-driven islands
The shape evolution of two-dimensional islands under electromigration-driven
periphery diffusion is studied by kinetic Monte Carlo (KMC) simulations and
continuum theory. The energetics of the KMC model is adapted to the Cu(100)
surface, and the continuum model is matched to the KMC model by a suitably
parametrized choice of the orientation-dependent step stiffness and step atom
mobility. At 700 K shape oscillations predicted by continuum theory are
quantitatively verified by the KMC simulations, while at 500 K qualitative
differences between the two modeling approaches are found.Comment: 7 pages, 6 figure
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