6,692 research outputs found
The atomic orbitals of the topological atom
The effective atomic orbitals have been realized in the framework of Bader’s atoms in molecules theory for a general wavefunction. This formalism can be used to retrieve from any type of calculation a
proper set of orthonormalized numerical atomic orbitals, with occupation numbers that sum up to the
respective Quantum Theory of Atoms in Molecules (QTAIM) atomic populations. Experience shows
that only a limited number of effective atomic orbitals exhibit significant occupation numbers. These
correspond to atomic hybrids that closely resemble the core and valence shells of the atom. The
occupation numbers of the remaining effective orbitals are almost negligible, except for atoms with
hypervalent character. In addition, the molecular orbitals of a calculation can be exactly expressed
as a linear combination of this orthonormalized set of numerical atomic orbitals, and the Mulliken
population analysis carried out on this basis set exactly reproduces the original QTAIM atomic populations of the atoms. Approximate expansion of the molecular orbitals over a much reduced set of
orthogonal atomic basis functions can also be accomplished to a very good accuracy with a singular
value decomposition procedure
BiFeO3/La0.7Sr0.3MnO3 heterostructures deposited on Spark Plasma Sintered LaAlO3 Substrates
Multiferroic BiFeO3 (BFO) / La0.7Sr0.3MnO3 heterostructured thin films were
grown by pulsed laser deposition on polished spark plasma sintered LaAlO3 (LAO)
polycrystalline substrates. Both polycrystalline LAO substrates and BFO films
were locally characterized using electron backscattering diffraction (EBSD),
which confirmed the high-quality local epitaxial growth on each substrate
grain. Piezoforce microscopy was used to image and switch the piezo-domains,
and the results are consistent with the relative orientation of the
ferroelectric variants with the surface normal. This high-throughput synthesis
process opens the routes towards wide survey of electronic properties as a
function of crystalline orientation in complex oxide thin film synthesis.Comment: 10 pages, 4 figures, Submitted to Applied Physics Letter
The electron-phonon coupling strength at metal surfaces directly determined from the Helium atom scattering Debye-Waller factor
A new quantum-theoretical derivation of the elastic and inelastic scattering
probability of He atoms from a metal surface, where the energy and momentum
exchange with the phonon gas can only occur through the mediation of the
surface free-electron density, shows that the Debye-Waller exponent is directly
proportional to the electron-phonon mass coupling constant . The
comparison between the values of extracted from existing data on the
Debye-Waller factor for various metal surfaces and the values known
from literature indicates a substantial agreement, which opens the possibility
of directly extracting the electron-phonon coupling strength in quasi-2D
conducting systems from the temperature or incident energy dependence of the
elastic Helium atom scattering intensities.Comment: 14 pages, 2 figures, 1 tabl
Multiple Sources toward the High-mass Young Star S140 IRS1
S140 IRS1 is a remarkable source where the radio source at the center of the
main bipolar molecular outflow in the region is elongated perpendicular to the
axis of the outflow, an orientation opposite to that expected if the radio
source is a thermal jet exciting the outflow. We present results of 1.3 cm
continuum and H2O maser emission observations made with the VLA in its A
configuration toward this region. In addition, we also present results of
continuum observations at 7 mm and re-analyse observations at 2, 3.5 and 6 cm
(previously published). IRS 1A is detected at all wavelengths, showing an
elongated structure. Three water maser spots are detected along the major axis
of the radio source IRS 1A. We have also detected a new continuum source at 3.5
cm (IRS 1C) located ~0.6'' northeast of IRS 1A. The presence of these two YSOs
(IRS 1A and 1C) could explain the existence of the two bipolar molecular
outflows observed in the region. In addition, we have also detected three
continuum clumps (IRS 1B, 1D and 1E) located along the major axis of IRS 1A. We
discuss two possible models to explain the nature of IRS 1A: a thermal jet and
an equatorial wind.Comment: 17 pages, 4 figures, to be published in A
Gold-catalyzed 1, 3-Thiazine formation and uncommon tautomer isolation
This work represents the first example of a gold-catalyzed formation of 1, 3-thiazine/1, 3-thiazinane by means of a catalytic approach and further uncommon isolation of the two tautomers. The developed protocol gives rise to a broad scope of 1, 3-thiazine derivatives with excellent yields in short reaction times. Interestingly, different isomers could be obtained depending on the state of the compound, and in the crystal state the 1, 3-thiazinane isomer is obtained, while in solution the 1, 3-thiazine is the unique isomer. This work represents an interesting approach for the synthesis of potential biologically relevant molecules and a crucial precedent in tautomerism isolation and characterization. © 2022 American Chemical Society. All rights reserved
Hydrodynamic View of Wave-Packet Interference: Quantum Caves
Wave-packet interference is investigated within the complex quantum
Hamilton-Jacobi formalism using a hydrodynamic description. Quantum
interference leads to the formation of the topological structure of quantum
caves in space-time Argand plots. These caves consist of the vortical and
stagnation tubes originating from the isosurfaces of the amplitude of the wave
function and its first derivative. Complex quantum trajectories display
counterclockwise helical wrapping around the stagnation tubes and hyperbolic
deflection near the vortical tubes. The string of alternating stagnation and
vortical tubes is sufficient to generate divergent trajectories. Moreover, the
average wrapping time for trajectories and the rotational rate of the nodal
line in the complex plane can be used to define the lifetime for interference
features.Comment: 4 pages, 3 figures (major revisions with respect to the previous
version have been carried out
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