Production and properties of metal-carbon composite coatings with a nanocrystalline structure

It is suggested to produce metal-carbon composite coatings by magnetron sputtering of mosaic cathodes, which are Group IV, V, and VI metals. The mosaic structure of the cathode elements are computer-optimized for each of the metals. Reflection electron diffraction studies show that the coatings have the amorphous or nanocrystalline structures, which are thermally stable. The coatings offer specific physical properties, in particular, low friction factor and high hardness.     

Polarization functions for the modified m6‐31G basis sets for atoms Ga through Kr

The 2df polarization functions for the modified m6‐31G basis sets of the third‐row atoms Ga through Kr (Int J Quantum Chem, 2007, 107, 3028; Int J. Quantum Chem, 2009, 109, 1158) are proposed. The performances of the m6‐31G, m6‐31G(d,p), and m6‐31G(2df,p) basis sets were examined in molecular calculations carried out by the density functional theory (DFT) method with B3LYP hybrid functional, Møller‐Plesset perturbation theory of the second order (MP2), quadratic configuration interaction method with single and double substitutions and were compared with those for the known 6‐31G basis sets as well as with the other similar 641 and 6‐311G basis sets with and without polarization functions. Obtained results have shown that the performances of the m6‐31G, m6‐31G(d,p), and m6‐31G(2df,p) basis sets are better in comparison with the performances of the known 6‐31G, 6‐31G(d,p) and 6‐31G(2df,p) basis sets. These improvements are mainly reached due to better approximations of different electrons belonging to the different atomic shells in the modified basis sets. Applicability of the modified basis sets in thermochemical calculations is also discussed. © 2013 Wiley Periodicals, Inc.     

Study of hyperfine interaction and electronic relaxation using coincidence Mössbauer spectroscopy

Coincidence Mössbauer spectroscopy (CMS) in the presence of a hyperfine field and electronic spin relaxation is discussed. The resulting expression for the transmission through a resonant absorber as a function of time is found with the help of the joint solution of the Maxwell equations and the density matrix equations. It is shown that the radiation that reaches the detector behind the absorber is modulated by the hyperfine field. The various polarization schemes for the CMS observation are analyzed. Numerical calculations were made for an⁵⁷ Fe nucleus.     

Large scale Hartree-Fock calculations with conventional SCF algorithm. Influence of integral and index compression on Fock matrix construction

It is shown that a compression of two-electron integrals and their indices significantly improves efficiency of the conventional self-consistent field (SCF) algorithm for a solution of the Hartree-Fock equation by decrease the Fock matrix calculation time. The improvement is reached not only due to a reduction of the integral file size, but mainly because data compression reduces or even can eliminate a cache conflict in data transfer from the hard drive to the main computer memory. Thus, the conventional SCF algorithm with the data compression becomes very efficient and permits to carry out large-scale Hartree-Fock calculations. The largest Hartree-Fock calculations have been performed for RNA 433D structure from the PDB data bank with 6080 basis functions formed from 6-31G basis on a workstation with 1 GHz Alpha processor.     

Narrow spectral lines of modulation harmonics of gamma radiation in unordered magnetic materials

The spectra of gamma-resonance lines excited using the amplitude modulation of the pumping field of the Mössbauer effect were studied in unordered magnetic materials with a strong spread of magnetic hyperfine fields at nuclei of Mössbauer isotopes. The analysis demonstrates that the spectra of modulation harmonics consist of narrow lines, and their form and intensity are determined by the contribution of magnetic local hyperfine fields, which are excited at a pumping frequency. The inversion of intensities for odd harmonics with the change in sign of detuning of the pumping frequency relative to the average Larmor frequency of the Mössbauer nucleus was noted. The application of this method to the spectral analysis of inhomogeneous magnetic materials is discussed.     

Accurate theoretical IR and Raman spectrum of Al2O2 and Al2O3 molecules

The accurate harmonic vibration frequencies together with the infrared (IR) and Raman intensities of the most stable conformers of Al₂O₂ and Al₂O₃ molecules have been calculated by the density functional theory (DFT) method with B3LYP exchange–correlation potential and using a set of the augmented correlated consistent basis sets up to quintuple order. The anharmonic vibration frequencies of the non-linear Al₂O₂ molecule have also been calculated. The obtained equilibrium geometrical parameters, harmonic and anharmonic vibration frequencies along with the IR and Raman intensities good converge to their limits with increasing the size of the used basis set. A comparison of the calculated harmonic and anharmonic vibrational frequencies with the available experimental ones points out that the small differences between the calculated harmonic and experimental frequencies can be further substantially reduced when calculations of the anharmonic vibrational frequencies will be available for all types of molecular geometries.     

Anomeric effect in N-azidomethylpyrrolidine: gas-phase electron diffraction and theoretical study

Gas-phase electron-diffraction data and high-level quantum chemical calculations have been used to study the conformational behaviour of N-azidomethylpyrrolidine. The two most stable conformers with a relative abundance of about 80% at 298 K possess gauche orientation of the azidomethyl group around the C-N(pyr) bond (C-N(azido)gauche with respect to the endocyclic N(pyr)-C bond). This orientation is a strong manifestation of an anomeric effect. The influence of the anomeric effect is also reflected in shortening of the C-N(pyr) bond and lengthening of the C-N(azido) bond as compared to such bonds in other compounds.     

Undecidability of the elementary theory of groups of measure-preserving transformations

The undecidability of the elementary theory of the automorphism group for a Lebesgue space is proved. It is shown that arithmetic can be interpreted in this theory. The technique of proof can be carried over to certain other groups. Translated fromMatematicheskie Zametki, Vol. 63, No. 3, pp. 414–420, March, 1998. The author wishes to thank the participants of the seminar on dynamical systems headed by D. V. Anosov, R. I. Grigorchuk, and A. M. Stepin as well as the participants of the Kolmogorov seminar of the Mechanics and Mathematics Department of Moscow State University for discussion of this work. The author is also indebted to N. K. Vereshchagin and A. M. Stepin for support and valuable remarks as well as to V. V. Ryzhikov for setting the problem and for his assistance.     

Induced resonant transparency of magnetic materials for gamma radiation: Propagation dynamics

The theory of spatiotemporal dynamics of gamma radiation in a resonant medium upon excitation of two-frequency gamma magnetic resonance in magnetic materials is considered. The radiation absorption at the fundamental frequency and the harmonic generation are investigated under conditions when the frequency of gamma radiation is shifted by the half-sum or half-difference of the frequencies of radio-frequency magnetic fields. It is shown that the propagation of gamma radiation through an absorber is characterized by a steady-state gamma intensity (resonant transparency). A consistent radio-frequency spectral analysis demonstrates that the intensities of harmonics drastically change at the transparency region boundaries due to nonlinear interference. The theory of quantum and dynamical beats of synchrotron radiation under conditions of induced resonant transparency is proposed.