An application of the DFT-based scaled quantum mechanical force field method to a weakly bonded system: N2O4

The adequacy of the density functional derived scaled quantum mechanical force field method of Rauhut and Pulay has been tested for a weakly bound dimer, N₂O₄. The Becke3–Lee–Yang–Parr/6-31G^* harmonic force field has been scaled with the transferable scale factors of Rauhut and Pulay (developed originally for `common' organic compounds without any reference to the N–O bond) resulting in 20.7 and 38 cm⁻¹ for the mean and the maximal individual deviations, respectively, as compared with experimental spectra. Consequently, the force field method of Rauhut and Pulay may give reliable results for non-common compounds as well.     

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.     

Structure of three-dimensional minimal parabolic surfaces in euclidean space

It is shown that the structure of a three-dimensional minimal parabolic surface is determined by the pair (V², γ), where V² is a minimal two-dimensional surface in Sⁿ and γ satisfies Δγ+2γ=0 (here Δ is the Laplace operator in ℝ⁴). It is also shown that the singularities of the surface are determined by zeros of γ. Bibliography: 9 titles. Published inZapiski Nauchnykh Seminarov POMI, Vol. 234, 1996, pp. 20–38.     

Exponential corrections to low-temperature expansion of 2D non-abelian models

The thermodynamic limit of certain exponential corrections to the weak coupling expansion of two-dimensional models is investigated. The expectation values of operators contributing to the first-order coefficient of the low-temperature expansion of the free energy are calculated for the order O(e^−β). They are proven to diverge logarithmically with the volume for non-abelian models.     

Explosive transition in amorphous microwire

An amorphous microwire in a glass shell offers a quick thermal response and can be rapidly heated to the crystallization point. When heated by a current pulse with a small amplitude and duration, the wire passes from the amorphous to microcrystalline state. The crystallization of the amorphous state may represent a slow or explosive process depending on the parameters of the pulse. In the latter case, the emission of electromagnetic waves (flash of light) and a sharp rise in the resistance are observed. The rate of propagation of the crystallization front in our experiments has been found to be about 1 m/s.     

Resistive switching and diode properties of mesoscopic niobium oxide-based structures

The bipolar effects of resistive switching (BRS) in mesoscopic heterostrucures based on amorphous and crystalline niobium oxide films are considered. The BRS effect is more pronounced in the structures based on multiphase nanocrystalline niobium oxide films. It is shown that the threshold frequency for observing the BRS effect is of the order of 10⁴ Hz. Switching is controlled via oxygen electrodiffusion to vacancies as the doping level of the contact area and the resistive properties of the heterocontact change.     

Effect of Zn and Ni impurities on the quasiparticle renormalization of superconducting Bi-2212

The Cu substitution by Zn and Ni impurities and its influence on the mass renormalization effects in angle-resolved photoelectron spectra (ARPES) of Bi2Sr2CaCu2O8-delta is addressed. We show that the nonmagnetic Zn atoms have a much stronger effect in both the nodal and antinodal parts of the Brillouin zone than magnetic Ni. The observed changes are consistent with the behavior of the spin resonance mode as seen by inelastic neutron scattering in YBCO. This strongly suggests that the "peak-dip-hump" and the kink in ARPES on the one side and neutron resonance on the other are closely related features.