On the donor-acceptor interaction and electron transfer at the titanium oxide-organic dye interface

The interface formed by a titanium oxide nanoparticle and a set of carboxyl molecules is quantum chemically considered as a chain of building blocks (with a limited size) in the form of binary molecular systems characterized by a strong donor-acceptor interaction. The ultrafast transfer of photoexcited electrons to the conduction band of titanium oxide is explained by the specific composition of the molecular orbitals of the system.     

The volt-ampere characteristic of a metal-semiconductor junction of small area,with the assumptions of diffusion theory

A metal-semiconductor junction was considered on the assumptions of diffusion theory, taking into account the presence of a gap between the metal and the semiconductor. A junction was chosen of area small enough for it to be possible to neglect the decrease due to recombination relative to the decrease due to divergence of the lines of flow. The volt-ampere characteristics and dependences of the injection coefficient on the voltage were obtained for the cases of low and high injection levels and slight or considerable band bending. It was shown that in all the cases indicated the nature of the dependence of the injection coefficient on the voltage (increasing or decreasing) depends essentially on the distribution of the voltage drop between the gap and the space charge region. Given certain relationships between the parameters of the semiconductor the latter dependence can take the form of a curve with a maximum.     

Quantum-chemical study of the interface formed by carboxylic species on TiO2 nanoparticles. 1. Nanoparticle surface

The current paper presents results of a quantum-chemical study of the surface structure of nanoparticles of both rutile and anatase crystallographic modifications. Different stages of the surface relaxation are discussed. Water adsorption is considered. The calculations were performed in the spd-basis by using semi-empirical quantum-chemical codes, both sequential and parallel. The results are mainly addressed to the study of the interface formed by titania nanoparticles and a set of carboxylated species, namely, benzoic, bi-isonicotinic acids as well as tris-(2,2′-dcbipyridine) Fe(II) complex placed on the surface of either rutile or anatase polymorphs.     

Local magnon modes and the dynamics of a small-radius two-dimensional magnetic soliton in an easy-axis ferromagnet

The internal dynamics of a small-radius precession magnetic soliton is considered. A variational formulation of the problem on the soliton-magnon interaction is proposed and used to calculate the frequency of a truly local mode. It is shown that this mode, as well as the conventional translational mode, remains localized in the small soliton radius limit. The presence of the local mode is confirmed by the numerical solution of the scattering problem.     

Vortex polarity switching by a spin-polarized current

The spin-transfer effect is investigated for the vortex state of a magnetic nanodot. A spin current is shown to act similarly to an effective magnetic field perpendicular to the nanodot. Then a vortex with magnetization (polarity) parallel to the current polarization is energetically favorable. Following a simple energy analysis and using direct spin-lattice simulations, we predict the polarity switching of a vortex. For magnetic storage devices, an electric current is more effective to switch the polarity of a vortex in a nanodot than the magnetic field.     

Neutron scattering study of reduced graphene oxide of natural origin

This paper presents a direct confirmation of graphene-like configuration and first suggests the chemical composition of basic structural elements of shungite attributing the latter to reduced graphene oxide nanosheets with an average 11:1:3 (C:O:H) atomic content ratio.     

Computational chemistry of the silicon nitride surface. 1. Water,ammonia, and water-ammonia complex

This paper deals with computational modeling of structure and properties of the silicon nitride surface zone using combined computational and real experiments. The computational experiment implies quantum chemical calculations of structure and vibrational spectra of polyatomic clusters. The real experiment suggests measurement and analysis of vibrational spectra. For quantum chemical calculations, semiempirical methods (MNDO and AM1) were chosen. In most calculations, the MNDO/H method was preferred because of the presence of many H-bonds in the surface zone. For verification of calculations, we calculated the structures and vibrational spectra of water and ammonia molecules and the water-ammonia complex and compared the results with experimental and ab initio (extended basis) data; MNDO/H proved to be an optimal method giving reliable results. Russian Peoples' Friendship University. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 1, pp. 58–69, January–February, 1995. Translated by L. Smolina     

“Chemical portrait” of fullerene molecules

Chemical activity of fullerene molecules is associated with a partially radical character of these molecules caused by the presence of effectively unpaired electrons (EUE). Values of the total number of N _D and partial distribution N _DA of EUE over the atoms in a singlet state of molecules C₆₀ and C₇₀ have been calculated. “Chemical portraits” of molecules are presented, and N _DA values are proposed to be used as indicators for chemical activity of atoms and to predict thereby the position of favorable atom-atom contacts in addition reactions with participation of these molecules. Bases of “computational synthesis” procedures for fullerene C₆₀ derivatives are exemplified by initial phases of its fluorination.     

The electronic states of naphthalene molecules adsorbed on a zeolite

Physical principles are considered for this method of examining interactions. Changes in absorption and fluorescence spectra are examined in relation to Van der Waals, electrostatic, and exchange interactions. Major spectral criteria are presented for the types of interaction and are illustrated by reference to naphthalene adsorbed on zeolites. Spectra at 77 K show that the adsorbed molecules are in two different states: in one they are bound by Van der Waals forces, while in the other a charge-transfer complex is formed. Examination at intervals after preparation shows that the adsorbed naphthalene is gradually oxidized.