964 research outputs found
Closed-shell interaction in silver and gold chlorides
Hartree-Fock and coupled-cluster calculations have been performed for cubic
AgCl and for AuCl having a cubic or the observed structure with space group
I4_1/amd. Cohesive energies and lattice constants are in excellent agreement
with experiment for AgCl; for AuCl we find good agreement, and the experimental
structure is correctly predicted to be lower in energy than the cubic one.
Electron-correlation effects on lattice constants are very large, of up to 0.8
\AA for cubic AuCl. We especially discuss the strength of the closed-shell
interactions, and for the first time a quantitative analysis of the so-called
"aurophilic" Au(I)-Au(I) interaction is presented in solids.Comment: accepted by J. Chem. Phy
Recurrence and differential relations for spherical spinors
We present a comprehensive table of recurrence and differential relations
obeyed by spin one-half spherical spinors (spinor spherical harmonics)
used in relativistic atomic, molecular, and
solid state physics, as well as in relativistic quantum chemistry. First, we
list finite expansions in the spherical spinor basis of the expressions
and
{}, where , , and
are either of the following vectors or vector operators:
(the radial unit vector), ,
(the spherical, or cyclic, versors),
(the Pauli matrix vector),
(the dimensionless
orbital angular momentum operator; is the unit matrix),
(the dimensionless
total angular momentum operator). Then, we list finite expansions in the
spherical spinor basis of the expressions
and
, where at least one of the objects
, , is the nabla operator
, while the remaining ones are chosen from the set
, , , ,
, .Comment: LaTeX, 12 page
Homogeneous Gold Catalysis through Relativistic Effects: Addition of Water to Propyne
In the catalytic addition of water to propyne the Au(III) catalyst is not
stable under non-relativistic conditions and dissociates into a Au(I) compound
and Cl2. This implies that one link in the chain of events in the catalytic
cycle is broken and relativity may well be seen as the reason why Au(III)
compounds are effective catalysts.Comment: 12 pages, 3 figures, 1 tabl
Symmetry and Electronic Structure of Noble Metal Nanoparticles and the Role of Relativity
High resolution photoelectron spectra of cold mass selected Cu_n-, Ag_n- and
Au_n- with n =53-58 have been measured at a photon energy of 6.42 eV. The
observed electron density of states is not the expected simple electron shell
structure, but seems to be strongly influenced by electron-lattice
interactions. Only Cu55- and Ag55- exhibit highly degenerate states. This is a
direct consequence of their icosahedral symmetry, as is confirmed by density
functional theory calculations. Neighboring sizes exhibit perturbed electronic
structures, as they are formed by removal or addition of atoms to the
icosahedron and therefore have lower symmetries. Gold clusters in the same size
range show completely different spectra with almost no degeneracy, which
indicates that they have structures of much lower symmetry. This behaviour is
related to strong relativistic bonding effects in gold, as demonstrated by ab
initio calculations for Au55-.Comment: 10 pages, 3 figure
Higher order Schrodinger and Hartree-Fock equations
The domain of validity of the higher-order Schrodinger equations is analyzed
for harmonic-oscillator and Coulomb potentials as typical examples. Then the
Cauchy theory for higher-order Hartree-Fock equations with bounded and Coulomb
potentials is developed. Finally, the existence of associated ground states for
the odd-order equations is proved. This renders these quantum equations
relevant for physics.Comment: 19 pages, to appear in J. Math. Phy
Embedding Transition-Metal Atoms in Graphene: Structure, Bonding, and Magnetism
We present a density-functional-theory study of transition-metal atoms (Sc–Zn, Pt, and Au) embedded in single and double vacancies (SV and DV) in a graphene sheet. We show that for most metals, the bonding is strong and the metal-vacancy complexes exhibit interesting magnetic behavior. In particular, an Fe atom on a SV is not magnetic, while the Fe@DV complex has a high magnetic moment. Surprisingly, Au and Cu atoms at SV are magnetic. Both bond strengths and magnetic moments can be understood within a simple local-orbital picture, involving carbon sp2 hybrids and the metal spd orbitals. We further calculate the barriers for impurity-atom migration, and they agree well with available experimental data. We discuss the experimental realization of such systems in the context of spintronics and nanocatalysis.Peer reviewe
A new online database of nuclear electromagnetic moments
Nuclear electromagnetic (EM) moments, i.e., the magnetic dipole and the electric quadrupole moments, provide important information of nuclear structure. As in other types of experimental data available to the community, measurements of nuclear EM moments have been organized systematically in compilations since the dawn of nuclear science. However, the wealth of recent moments measurements with radioactive beams, as well as earlier existing measurements, lack an online, easy-to-access, systematically organized presence to disseminate information to researchers. In addition, available printed compilations suffer a rather long life cycle, being left behind experimental measurements published in journals or elsewhere. A new, online database (http://magneticmoments.info) focusing on nuclear EM moments has been recently developed to disseminate experimental data to the community. The database includes non–evaluated experimental data of nuclear EM moments, giving strong emphasis on frequent updates (life cycle is 3 months) and direct connection to the sources via DOI and NSR hyperlinks. It has been recently integrated in IAEA LiveChart [1], but can also be found as a standalone webapp [2]. A detailed review of the database features, as well as plans for further development and expansion in the near future is discussed
Cohesive properties of alkali halides
We calculate cohesive properties of LiF, NaF, KF, LiCl, NaCl, and KCl with
ab-initio quantum chemical methods. The coupled-cluster approach is used to
correct the Hartree-Fock crystal results for correlations and to systematically
improve cohesive energies, lattice constants and bulk moduli. After inclusion
of correlations, we recover 95-98 % of the total cohesive energies. The lattice
constants deviate from experiment by at most 1.1 %, bulk moduli by at most 8 %.
We also find good agreement for spectroscopic properties of the corresponding
diatomic molecules.Comment: LaTeX, 10 pages, 1 figure, accepted by Phys. Rev.
g factor of Li-like ions with nonzero nuclear spin
The fully relativistic theory of the g factor of Li-like ions with nonzero
nuclear spin is considered for the (1s)^2 2s state. The magnetic-dipole
hyperfine-interaction correction to the atomic g factor is calculated including
the one-electron contributions as well as the interelectronic-interaction
effects of order 1/Z. This correction is combined with the
interelectronic-interaction, QED, nuclear recoil, and nuclear size corrections
to obtain high-precision theoretical values for the g factor of Li-like ions
with nonzero nuclear spin. The results can be used for a precise determination
of nuclear magnetic moments from g factor experiments.Comment: 20 pages, 5 figure
Elastic and vibrational properties of alpha and beta-PbO
The structure, electronic and dynamic properties of the two layered alpha
(litharge) and beta (massicot) phases of PbO have been studied by density
functional methods. The role of London dispersion interactions as leading
component of the total interaction energy between layers has been addressed by
using the Grimme's approach, in which new parameters for Pb and O atoms have
been developed. Both gradient corrected and hybrid functionals have been
adopted using Gaussian-type basis sets of polarized triple zeta quality for O
atoms and small core pseudo-potential for the Pb atoms. Basis set superposition
error (BSSE) has been accounted for by the Boys-Bernardi correction to compute
the interlayer separation. Cross check with calculations adopting plane waves
that are BSSE free have also been performed for both structures and vibrational
frequencies. With the new set of proposed Grimme's type parameters structures
and dynamical parameters for both PbO phases are in good agreement with
experimental data.Comment: 8 pages, 5 figure
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