Filled Electron Shells Research Articles

Spontaneous Appearance of Nanoclusters (Cu)n and (Cu2O)n

In this article, we proceed to the performance properties of the nanoclusters, referring to the already changing their properties associated with the size impact. Consideration of size effects we start to build models of nanoclusters, which reflect changes in the dynamic stability of atomic clusters, structural and electronic properties. The observed properties will be considered in comparison with model calculations and predictions. The process of formation of this cluster is accompanied by a discontinuity of symmetry, which can be distinguished on the specific structure of the cluster. Clusters of the (Cu)n metals should have the simplest electronic structure with one s-electron in each atom over the filled electron shells and (Cu2O)n semiconductors with more complicated p–n transition.

The Influence of Carbon Doping on the Structures, Properties, and Stability of Beryllium Clusters

The global minimum structures of the carbon‐doped Ben (n = 1–12) clusters are obtained at the B3PW91/6‐311+G(d) level and compared with those of pure beryllium clusters. It is found that the carbon dopant prefers to be located outside the host Ben cage and tends to be tetracoordinated. The evolution of the electronic and energetic properties of BenC is studied using the QCISD(T) method. Results show that the introduction of carbon doping strengthens intracluster interaction of beryllium clusters. Besides, the Be3C and Be8C clusters, with their particular stability, are considered as magic‐number clusters in the BenC series. Molecular‐orbital (MO) analysis indicates that both clusters have fully filled electron shells, whereas the contribution of the carbon atomic orbital leads to MO energy‐level disorder of the BenC clusters.

High Z effects in accounting for radiative component of the electron magnetic moment in hydrogen-like atoms

The behavior of electron energy levels in hydrogen-like atoms is studied while taking into account the nonperturbative interaction between the radiative component of the magnetic moment of a free electron Δgfree and the Coulomb field of an atomic nucleus with charge Z, including those with Z > 137. It is shown that for Zα ≪ 1 the energy-level shift is rather effectively determined through the matrix elements of the corresponding Dirac-Pauli operator with relativistic Coulomb wave functions. At the same time, for superheavy nuclei with Z ∼ 170, this shift, generated by Δgfree, is genuinely nonperturbative, behaves like ∼Z5 near the threshold of negative continuum, exceeds all the estimates of radiative corrections coming from vacuum polarization and electron self-energy known so far, and turns out to be at least of the same order as the effects of nuclear charge screening by filled electron shells.

The coulomb glory effect in collisions of antiprotons with heavy ions

The Coulomb glory effect in the back scattering of antiprotons with energies of from 100 eV to 3 keV from a bare nucleus of uranium and from uranium ions with closed shells is considered in terms of nonrelativistic and relativistic quantum theory. The appearance of Coulomb glory in collisions with multiply charged ions is caused by nucleus charge screening by filled electron shells. In scattering from a bare nucleus, the effect appears because of the screening properties of the vacuum polarization potential.

Throwing jellium at gallium—a systematic superatom analysis of metalloid gallium clusters

Motivated by recent developments in the field of so-called "superatom complexes", as well as by the challenge posed to theory in understanding the many polymorphs of gallium, we analyse the electronic structure of several previously synthesised ligand-protected gallium clusters and their model derivatives using density functional theory. The calculated electron charge densities within the respective gallium cores are shown to be consistent with the jellium superatom model, exhibiting well-defined global spherical shells and wide HOMO-LUMO gaps--indicating enhanced chemical stability. It is demonstrated that the HOMO-LUMO gaps are widened due to the presence of covalent gallium-ligand bonds and a closed electron shell (i.e. electron "magic" number). The tendency of retaining a filled electron shell is shown to be particularly apparent in two closely-related clusters, with one derived from the other simply via substituting a doubly negative charge by a single protective moiety containing a lone electron pair. This analysis verifies that spherical electron shells can influence the chemical stability of ligand-protected gallium clusters, and also demonstrates the significant stabilising effects of metal-ligand interactions-something that is poorly accounted for in the current superatom model.

Magnetoreception

Few subjects in animal behavior have more exotic mystery than magnetic-field sensitivity. A force we cannot sense, generated by events no one completely understands, creates field lines that pass through our bodies without any evident effect on us or on them. It is an energy felt as much by migrating lobsters on the sea floor as by ocean-crossing birds thousands of meters overhead, transduced in generally poorly understood ways. Despite the blindness of humans, modern life depends on this invisible, ghostlike field. Aside from lights and heaters, nearly every electrical device we own makes use of electromagnetism, and that same magnetism is essential in generating the power these new-found necessities consume. But for many animals, the reliance is far older and more basic: their life-or-death ability to find their way around in the world depends on correctly interpreting the earth's magnetic field.

The linear dependence of the term energy on quantum defects in ions with completely filled electron shells and its application for calculating parameters of the smooth nonlocal model potential

The energy levels of the valence electrons of free ions with completely filled electron shells are analyzed. A linear correlation between term energies E nl and quantum defects dn nl is assumed to exist at constant values of orbital quantum numbers and ion charges for the Li, Na, Cu, Ag, and Au rows. The empirical dependence of quantum defects dn nl on the principle quantum number n is found. It can be used to estimate unknown term energies. It is also demonstrated that the linear dependences of the smooth nonlocal model pseudopotential parameter A nl of free ions on the term energy E nl is the result of their linear dependences on quantum defects dn nl .

Magnetic superatoms

Clusters of atoms are generally only stable enough to form superatoms when they have filled electron shells, so how can they have magnetic properties?

Polaron shift for intercalation compounds of titanium dichalcogenides

The data available in the literature on the magnitude and character of the lattice deformation upon intercalation of transition metals and silver into titanium dichalcogenides are analyzed, and the stability condition for the localization of charge carriers in the form of polarons is determined. It is shown that the stability of polarons is determined by the competition between the gain in the free energy of the electronic subsystem and the quasi-elastic contribution associated with the interaction of filled electron shells of intercalant ions and atoms of the nearest environment.

Periodicity in 6Li-to-7Li Isotopic Reduced Partition Function Ratios of Diatomic Lithium Compounds

The UB3LYP/LanL2DZ level calculations were carried out for sixty-seven Li-M diatomic molecules of lithium between LiH and LiBi to explore the periodic properties of their 6Li-to-7Li isotopic reduced partition function ratios (rpfrs) and some other quantities. The Li-M bond distance, the frequency shift upon 7Li/6Li isotope substitution and the rpfr all show plots typical of any chemical and physical property which is a periodic function of the atomic number. The rpfr is strongly correlated with the Li-M bond stretching force constant except for LiH. The present calculations show that the rpfrs of diatomic molecules of group 2, group 12 and group 18 elements are relatively small, which reflects the filled electron shell and subshell characters of those elements. The results of the calculations and the consideration on chemical properties of elements suggest that zinc is a possible substitute for mercury in lithium isotope separation processes utilizing the redox reaction of lithium.

The Smaller Fullerene C50, Isolated as C50Cl10.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Extremely stable metal-encapsulated AlPb10+ and AlPb12+ clusters: mass-spectrometric discovery and density functional theory study.

We report the experimental discovery of extremely stable metal-encapsulated superatom clusters of a group IVA element: AlPb+10 and AlPb+12. Ab initio density functional geometry optimizations at the B3LYP/LANL2DZ level result in a perfect icosahedron with an exceptionally large HOMO-LUMO gap of 3.1 eV for AlPb+12, and a related structure with D(4d) symmetry for AlPb+10, with a HOMO-LUMO gap of 2.6 eV. Their high stability is attributed to the reinforcing influence of the most favorable closed-packed structure and optimally filled electron shells.

Luminescence of impurity-bound excitons in corundum

The luminescence characteristics of M3+: Al2O3 crystals, where M3+ stands for an isoelectronic cation impurity with a filled electron shell, namely, Sc3+, Y3+, or La3+, were studied. The luminescence of excitons bound (BE) to these impurities was detected. The position of the BE energy states at the long-wavelength absorption edge as a function of the M3+ ionic radius was established. The energies of the long-wavelength BE creation threshold and of the maximum of the BE luminescence band were approximated empirically by third-order polynomials of the Toyozawa polynomial type, which describes electron-phonon interaction. The energy and spatial structure of the BE was found to be similar to that of a self-trapped exciton (STE). The BE and STE states are separated by an energy barrier, and energy transfer from the STE to BE is frozen at low temperatures.

Ionization loss of relativistic structural heavy ions in collisions with atoms

A nonperturbative theory of energy loss in collisions between structural, highly charged heavy ions moving at relativistic velocities and atoms is developed. A simple formula for effective deceleration is derived. By structural ions are meant ions containing partially filled electron shells. It is such ions characterized, as a rule, by a significant charge (for example, partially “stripped” uranium ions) that are used in numerous experiments involving the use of modern heavy-ion accelerators.

Spin and orbital contributions to the magnetic scattering of neutrons

The current densities in partially filled electron shells of free atoms or ions, when analyzed in terms of multipole expansions, do not carry signatures that would distinguish orbital and spin currents. The same holds for the orbital and spin contributions to elastic neutron scattering amplitude, which are related to Fourier transforms of the respective current densities. The pitfalls of the so-called dipole approximation, which appears to enable a distinction, are pointed out and errors involved are calculated for some free-ion and crystal-field states.

Shell Dependent Chemical Reactivity of Large Sodium Clusters

It has been shown in the past that sodium clusters possess an electronic shell structure characteristic of a nearly spherical, finite Fermi system. For this reason they might be expected to behave like giant atoms. In fact, closed shell clusters are known to have particularly high ionization energies. In this paper, we report variations in the reactivity of Nan for 100 ≤ n ≤ 800 with molecular oxygen. Clusters with completely filled electron shells are found to be relatively unreactive.

Negative Calcium Ions Are Stable—In Spite of the Conventional Wisdom

Most atomic species—roughly 80% of the periodic table—can form stable negative ions in their gaseous phase. The most notable and easily understood exceptions are the noble gas atoms, the symmetry of whose completely filled electron shells offers no handhold for a would-be extra tenant. The alkaline earths—calcium, strontium, barium and their group IIA cousins—are similarly inhospitable, or so the standard textbooks assure us. Two back-to-back reports in a recent issue of Physical Review Letters have now disabused us of this venerable assurance.

Parameters of bound multiexciton complexes in direct polar semiconductors

AbstractUsing a generalized density‐functional method, which takes electron–phonon interaction into account, the ground state energies of donor BMEC's D0Xm(m = 1,…, 20) are calculated for the polar semiconductors ZnS, CdS, and CdSe. The highest stability is obtained for complexes possessing filled electron shells (m = 1, 7, 19), whereas gaps of instability are located between these complexes. The spectral locations of luminescence lines connected with the radiative decay of BMEC's are predicted and found to be concentrated between the luminescence lines of the bound exciton and the free exciton. Furthermore, analytic approximate expressions for the electron and hole densities are obtained and their shapes are extensively discussed.

Luminescence from Bound Multiexcition Complexes (BMEC) in direct polar semiconductors

Localization energies and luminescence line positions for BMEC's in direct polar semiconductors are theoretically investigated. Our results for bound polaron and bound exciton exhibit excellent agreement with the best ones known from literature. In case of higher complexes significant stability is obtained for filled electron shells ( m=1,7,19), whereas gaps of instability are located between them. Luminescence lines are located between free exciton and bound exciton lines.

Correlations between ESCA chemical shifts and modified sanderson electronegativity calculations

Correlations are given between ESCA chemical shifts and partial atomic changes calculated by the modified Sanderson method. Elements included are boron, carbon, silicon, germanium, tin, nitrogen, phosphorus, arsenic, oxygen, sulfur, selenium, fluorine, chlorine and bromine. Successful correlations were obtained for most elements; the best success was for situations involving a constant number of σ bonds. The method was least successful for nitrogen, oxygen, chlorine and bromine. The modified Sanderson method performed comparably to CNDO and Jolly electronegativity calculations in most cases. Correction for molecular potential is automatically achieved using the modified Sanderson method. When the data for all elements are considered the MS model seems to work reasonably well. Correlations for B, C, Ge, F, N, As and Se seem to be as good as most methods applied to these elements. The MS method works particularly well for Si, Sn, P and S. It is inapplicable to O, Cl and Br. For compounds of elements which exist in more than one formal oxidation state, it is necessary to obtain a separate plot of E B, versus q i for each oxidation state. Once this is done, the calculated and experimental binding energies show good correlation. The slopes and intercepts given in Table 3 may be used for this purpose. The reason for separate correlation lines in the case of multiple oxidation states may be understood when one considers the method by which Sanderson originally calculated his atomic E values. Sanderson's original E values were calculated as the ratio of the electron density of an element stripped of all its valence electrons to the electron density of the corresponding inert gas. By considering only the inert shell configuration, Sanderson's E values are valid for filled electron shell oxidation states. However, no allowance for lone electron pairs is made. Thus, charges calculated by Sanderson's method for elements bound in less than their maximum oxidation state may not be correct relative to other oxidation states of the same element. Attempts to correct for this neglect of lone pairs were made during the course of this work by assigning E values for an electron pair or by calculating E values for non-inert shell valence configurations met with failure. The low slopes of the binding energy-charge correlations for oxygen and the halogens may also be explained by the method Sanderson used to calculate his atomic E values. Sanderson assumed that all elements shared all valence electrons in bonding. This is not the case for the halogens or oxygen which retain essentially inert lone electron pairs. Since the effect of these lone pairs is not specifically dealt with, the charges calculated by Sanderson's method and the MS method are larger than they should be in the case of elements which retain nonbonded lone pairs.Throughout these studies, it has been noted that the MS method needs no correction for molecular potential. This may be explained by the manner in which group E values are calculated. Since the electronegativities of the atoms comprising a group are “sequentially” equalized from the terminal atom of a group inward to the site of the central atom, through bond inductive effects are accounted for. This procedure reduces a multiatom group to a form in which it may be treated as a single atom attached to the atom of interest. In this form, a molecule is reduced to Pauling's “nearest neighbor” picture. Thomas 19 has found that Pauling's “nearest neighbor” approximation works well for correlating ESCA data of small (e.g. methane-line) molecules without additional correction for molecular potential. Thus, the MS method has reduced a molecule to a form where the “nearest neighbor” approximation is applicable. The MS method works well for covalent molecules. As was pointed out earlier, the method fails for ionic solids primarily because of anomalies introduced by the Madelung potential. It is speculated that the MS method will work well for isolated ionic molecules in the gas-phase.