Formation and growth of an α-PbF2 phase during the plastic deformation of β-PbF2 crystals

The microstructure of strained β-PbF₂ crystals is investigated by optical and scanning electron microscopy. It is established that the α-PbF₂ previously observed by x-ray diffraction methods during the straining of cubic PbF₂ nucleates predominantly on structural defects like slip lines and bands. The kinetics of the growth of α-PbF₂ particles during the straining of β-PbF₂ crystals and during a postdeformation anneal is investigated. The results of the experiments point to the involvement of diffusion in the growth of α-PbF₂. Fiz. Tverd. Tela (St. Petersburg) 39, 640–646 (April 1997)     

Correlation of the chemical shifts of the NMR of n14 in nitro compounds with the frequencies of antisymmetric valence vibrations of the nitro group in the ir spectra

Conclusions The correlational relation between the chemical shift of the NMR of the N¹⁴ nitrogen and frequencies of antisymmetric valence vibrations of the nitro group in the IR spectra of nitro compounds was found.Translated from Izvestiya Academii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 675–676, March, 1968.     

The molecular structure of tetra-tert-butyldiphosphine: an extremely distorted, sterically crowded molecule

The molecular structure of tetra-tert-butyldiphosphine has been determined in the gas phase by electron diffraction using the new DYNAMITE method and in the crystalline phase by X-ray diffraction. Ab initio methods were employed to gain a greater understanding of the structural preferences of this molecule in the gas phase, and to determine the intrinsic P-P bond energy, using recently described methods. Although the P-P bond is relatively long [GED 226.4(8) pm; X-ray 223.4(1) pm] and the dissociation energy is computed to be correspondingly small (150.6 kJ mol(-1)), the intrinsic energy of this bond (258.2 kJ mol(-1)) is normal for a diphosphine. The gaseous data were refined using the new Edinburgh structure refinement program ed@ed, which is described in detail. The molecular structure of gaseous P(2)Bu(t)(4) is compared to that of the isoelectronic 1,1,2,2-tetra-tert-butyldisilane. The molecules adopt a conformation with C(2) symmetry. The P-P-C angles returned from the gas electron diffraction refinement are 118.8(6) and 98.9(6) degrees, a difference of 20 degrees, whilst the C-P-C angle is 110.3(8) degrees. The corresponding parameters in the crystal are 120.9(1), 99.5(1) and 109.5(1) degrees. There are also large deformations within the tert-butyl groups, making the DYNAMITE analysis for this molecule extremely important.     

Behaviour of implanted arsenic in silicon single crystals subjected to transient heating with incoherent light

The behaviour of ion-implanted arsenic in 100-oriented silicon single crystals exposed to continuous incoherent light from a xenon arc lamp has been analyzed with sheet resistivity measurements, Rutherford backscattering spectrometry, and ion channeling including angular scans. Redistribution, substitutionality, and electrical activity of arsenic were followed as functions of exposure time (6–20s) and induced temperature (1000°–1100°C). Redistribution was observed for implanted concentrations exceeding 4×10²⁰ at.%/cm³. High substitutional fractions, between 95% and 99%, and low sheet resistivities were found for all annealed samples. Formation mechanism of arsenic substitutional solid solutions during transient heating of implanted layers is discussed.     

Thermal Degradation of Polyvinylpyrrolidone on the Surface of Pyrogenic Silica

Thermal degradation of polyvinylpyrrolidone was studied by thermogravimetry, IR spectroscopy, and thermal-desorption mass spectrometry.     

Photoelectron spectra and electronic structure of aza-boron-dipyridomethene derivatives

The electronic structure of three aza-boron-dipyridomethene derivatives containing different hydrocarbon groups at the boron atom is studied by ultraviolet photoelectron spectroscopy and calculations at the density functional theory level. According to the experimental and theoretical data, the higher occupied molecular orbitals of anthracene, acridine, and the studied complexes are of the same character. For the three studied compounds, the effect of alkyl and phenyl substituents on the electronic structure is determined. The parameters of the electronic structure of aza-boron-dipyridomethene (phenyl groups at the boron atom) and its β-diketonate analogue are compared. It is shown that in an energy range up to 11 eV the calculated results correlate with the ultraviolet photoelectron spectra.