Fourier-synthesis approach for static charge-density reconstruction from theoretical structure factors of CaB6

In a pilot study, electron-density (ED) and ED Laplacian distributions were reconstructed for the challenging case of CaB₆ (Pearson symbol cP7) with conceptually fractional B-B bonds from quantum-chemically calculated structure-factor sets with resolutions 0.5 Å^-1 ≤ [sin(θ)/λ]_max ≤ 5.0 Å^-1 by means of Fourier-synthesis techniques. Convergence of norm deviations of the distributions obtained with respect to the reference ones was obtained in the valence region of the unit cell. The QTAIM (quantum theory of atoms in molecules) atomic charges, and the ED and ED Laplacian values at the characteristic critical points of the Fourier-synthesized distributions have been analysed for each resolution and found to display a convergent behaviour with increasing resolution. The presented method(exponent) (ME) type of Fourier-synthesis approach can qualitatively reconstruct all characteristic chemical bonding features of the ED from valence-electron structure-factor sets with resolutions of about 1.2 Å^-1 and beyond, and from all-electron structure-factor sets with resolutions of about 2.0 Å^-1 and beyond. Application of the ME type of Fourier-synthesis approach for reconstruction of ED and ED Laplacian distributions at experimental resolution is proposed to complement the usual extrapolation to infinite resolution in Hansen-Coppens multipole model derived static ED distributions.

Interacting Quantum Atoms Method for Crystalline Solids

An implementation of the Interacting Quantum Atoms method for crystals is presented. It provides a real space energy decomposition of the energy of crystals in which all energy components are physically meaningful. The new package ChemInt enables one to compute intra-atomic and inter-atomic energies, as well as electron population measures used for quantitative description of chemical bonds in crystals. The implementation is tested and applied to characteristic molecular and crystalline systems with different types of bonding.

Laser-induced damage investigation at 1064 nm in KTiOPO4 crystals and its analogy with RbTiOPO4

Bulk laser-induced damage at 1064 nm has been investigated in KTiOPO4 (KTP) and RbTiOPO4 (RTP) crystals with a nanosecond pulsed Nd:YAG laser. Both crystals belong to the same family. Throughout this study, their comparison shows a very similar laser-damage behavior. The evolution of the damage resistance under a high number of shots per site (10,000 shots) reveals a fatigue effect of KTP and RTP crystals. In addition, S-on-1 damage probability curves have been measured in both crystals for all combinations of polarization and propagation direction aligned with the principal axes of the crystals. The results show an influence of the polarization on the laser-induced damage threshold (LIDT), with a significantly higher threshold along the z axis, whereas no effect of the propagation direction has been observed. This LIDT anisotropy is discussed with regard to the crystallographic structure.

Laser damage resistance of RbTiOPO(4): evidence of polarization dependent anisotropy

Nanosecond-laser induced damage of RbTiOPO(4) crystals (RTP) has been studied at 1064 nm as a function of propagation direction and polarization orientation. A significant difference in the Laser Induced Damage Threshold (LIDT) was observed for x-cut and y-cut crystals in Pockels cell configuration, where the light propagation direction is along the x and y axes of the crystal respectively. In Pockels cell configuration the polarization is oriented at 45? with respect to the z-axis of the crystal. Experiments with the polarization oriented parallel to the principal axes of the crystal pointed out the importance of the polarization direction for the LIDT whereas the propagation direction did not significantly influence the LIDT. Comparison of the experimental data with a simple model reveals the influence of frequency doubling on the LIDT in Pockels cell configuration. In the case of the y-cut Pockels cell, the generation of frequency doubled light causes an LIDT below the LIDT of x and z-polarized light at the fundamental wavelength.

Electron Localization Function in Full-Potential Representation for Crystalline Materials

The electron localization function (ELF) is implemented in the first-principles, all-electron, full-potential local orbital method. This full-potential implementation increases the accuracy with which the ELF can be computed for crystalline materials. Some representative results obtained are presented and compared with the results of other methods. Although for crystal structures with directed bonding only minor differences are found, in simple elemental metals, there are differences in the valence region, which give rise to different ELF topologies.

Metal-metal bonding in ScTaN2. A new compound in the system ScN-TaN

Gray microcrystalline powders of ScTaN(2) were prepared from solid-state reactions of delta-ScN with Ta(3)N(5) powders at T = 1770 K. According to thermal analyses the compound is stable against oxidation by O(2) up to temperatures of T = 800 K. In an Ar atmosphere ScTaN(2) decomposes above T = 1250 K and in a N(2) atmosphere above T = 2000 K under release of N(2) to form delta-ScN and beta-Ta(2)N. The crystal structure (space group P6(3)/mmc, No. 194, a = 305.34(3) pm, c = 1056.85(9) pm, Z = 2) was refined on the basis of X-ray and neutron powder diffraction data. It comprises alternating layers of ScN(6/3) octahedra and trigonal TaN(6/3) prisms, which are also observed in the binary nitrides delta-ScN and theta-TaN, respectively. A small degree of anti-site defects (about 5%) was detected. Only a small solubility of ScN in epsilon-TaN was observed, while the solubility of TaN in delta-ScN is >/=10 mol % at T = 1820 K. ScTaN(2) is a diamagnetic small gap semiconductor or a semimetal, as inferred from magnetization and electrical resistivity measurements, consistent with band structure calculations. Chemical bonding analyses with the COHP method yield significant covalent Ta-Ta interactions. Topological analyses of the electron localization function reveal unexpected Ta-Ta three-center bonding basins within seemingly empty trigonal prisms of the TaN(6/3) layers.

Metal−Metal Bonding in ScTaN2. A New Compound in the System ScN−TaN

Gray microcrystalline powders of ScTaN(2) were prepared from solid-state reactions of delta-ScN with Ta(3)N(5) powders at T = 1770 K. According to thermal analyses the compound is stable against oxidation by O(2) up to temperatures of T = 800 K. In an Ar atmosphere ScTaN(2) decomposes above T = 1250 K and in a N(2) atmosphere above T = 2000 K under release of N(2) to form delta-ScN and beta-Ta(2)N. The crystal structure (space group P6(3)/mmc, No. 194, a = 305.34(3) pm, c = 1056.85(9) pm, Z = 2) was refined on the basis of X-ray and neutron powder diffraction data. It comprises alternating layers of ScN(6/3) octahedra and trigonal TaN(6/3) prisms, which are also observed in the binary nitrides delta-ScN and theta-TaN, respectively. A small degree of anti-site defects (about 5%) was detected. Only a small solubility of ScN in epsilon-TaN was observed, while the solubility of TaN in delta-ScN is >/=10 mol % at T = 1820 K. ScTaN(2) is a diamagnetic small gap semiconductor or a semimetal, as inferred from magnetization and electrical resistivity measurements, consistent with band structure calculations. Chemical bonding analyses with the COHP method yield significant covalent Ta-Ta interactions. Topological analyses of the electron localization function reveal unexpected Ta-Ta three-center bonding basins within seemingly empty trigonal prisms of the TaN(6/3) layers.

Large orbital moments and internal magnetic fields in lithium nitridoferrate(I)

The iron nitridometalates Li2[(Li(1-x)Fe(I)(x))N] display ferromagnetic ordering and spin freezing. Large magnetic moments up to 5.0mu(B)/Fe are found in the magnetization. In Mössbauer effect studies huge hyperfine magnetic fields up to 696 kOe are observed at specific Fe sites. These extraordinary fields and moments originate in an unusual ligand field splitting for those Fe species leading [within local spin density approximation (LSDA)] to a localized orbitally degenerate doublet. Including spin-orbit interaction and strong intra-atomic electron correlation (LDA+SO+U) gives rise to a large orbital momentum.

Li24[MnN3]3N2 and Li5[(Li1-xMnx)N]3, two intermediates in the decomposition path of Li7[MnN4] to Li2[(Li1-xMnx)N]: an experimental and theoretical study

The crystal structure of Li7[Mn(V)N4] was re-determined. Isolated tetrahedral [Mn(V)N4](7-) ions are arranged with lithium cations to form a superstructure of the CaF2 anti-type (P4bar3n, No. 218, a = 956.0(1) pm, Z = 8). According to measurements of the magnetic susceptibility, the manganese (tetrahedral coordination) is in a d(2) S = 1 state. Thermal treatment of Li7[Mn(V)N4] under argon in the presence of elemental lithium at various temperatures leads to Li24[Mn(III)N3]3N2, Li5[(Li1-xMnx)N]3, and Li2[(Li1-xMn(I)x)N], respectively. Li24[Mn(III)N3]3N2 (P3bar1c, No. 163, a = 582.58(6) pm, c = 1784.1(3) pm, Z = 4/3) crystallizes in a trigonal unit cell, containing slightly, but significantly nonplanar trigonal [MnN3](6-) units with C3v symmetry. Measurements of the magnetic susceptibility reveal a d(4) S = 1 spin-state for the manganese (trigonal coordination). Nonrelativistic spin-polarized DFT calculations with different molecular models lead to the conclusion that restrictions in the Li-N substructure are responsible for the distortion from planarity of the [Mn(III)N3](6-). Li5[(Li1-xMnx)N]3 (x = 0.59(1), P6bar2m, No. 189, a = 635.9(3) pm, c = 381.7(2) pm, Z = 1) is an isotype of Li5[(Li1-xNix)N]3 with manganese in an average oxidation state of about +1.6. The crystal structure is a defect variant of the alpha-Li3N structure type with the transition metal in linear coordination by nitrogen. Li2[(Li1-xMn(I)x)N] (x = 0.67(1), P6/mmm, No. 191, a = 371.25(4) pm, c = 382.12(6) pm, Z = 1) crystallizes in the alpha-Li3N = Li2[LiN] structure with partial substitution of the linearly nitrogen-coordinated Li-species by manganese(I). Measurements of the magnetic susceptibility are consistent with manganese (linear coordination) in a low-spin d(6) S = 1 state.

A measure of individual sense of competence

A paper-and-pencil instrument to measure an individual's “sense of competence” or his basic psychological feelings of confidence and competence resulting from mastery of his environment is developed in this research. The content validity of the instrument is demonstrated based on the interpretation of four factors extracted from factor analysis and the subsequent analytic oblique solution. The predictive validity of the instrument is strongly supported by two separate studies conducted by two different groups of researchers. Internal reliability is also tested and found to be satisfactory. Finally, the implications of the new instrument for future research, especially in organizational and work settings, are discussed.