Formation and Decomposition of the Methylplatinum(IV) Complex in the Mechanically Activated K2PtCl4 Powder–MeI Vapor System

Mechanical treatment of the K₂PtCl₄ solid salt in a vibrating mill results in Pt–Cl bond heterolysis to form coordinatively unsaturated Pt(II) complexes. At room temperature, the freshly treated K₂PtCl₄ salt absorbs methyl bromide and evolves methyl chloride to the gas phase. The reaction mechanism involves the following sequence of steps: the oxidative addition of methyl iodide to Pt(II) with the intermediate formation of Pt(IV) methyl complexes and the decomposition of the latter due to intramolecular reductive elimination with methyl chloride formation. The first step of the reaction of MeI with the preactivated surface of the K₂PtCl₄ salt is assisted by active sites, which are regenerated in each act of the chemical transformation of MeI into MeCl involving in the chain substitution of halogen in methyl iodide. The coordinatively unsaturated surface platinum complexes can act as such active sites. Due to their effective positive charge, they can provide electrophilic assistance to nucleophilic substitution. Chain termination is probably due to the coordination of the complex with a coordination vacancy and an interstitial chloride ion to the inactive K₂PtCl₄ complex.     

High-Speed Composite Microactuator Based on Ti<Subscript>2</Subscript>NiCu Alloy with Shape Memory Effect

Samples of microactuators are made of a bimorph composite of Ti₂NiCu alloy with a thermoelastic martensitic transition and the shape memory effect, and their response rate is investigated. The active layer of the composite actuator is a layer of the rapidly quenched Ti₂NiCu alloy, pseudoplastically prestretched, and an amorphous layer of the same alloy is used as an elastic layer. Typical sizes of the microactuator are 30 × 2 × 2 μm. The controlled amplitude of the displacement of the microactuator tip is approximately 1 μm. The response rate of the microactuator was investigated by scanning electron microscopy. Activation of the microactuator was achieved by heating when electric pulses were passed through it. Full activation of the microactuator at frequencies up to 1 kHz was demonstrated; partial activation was observed at frequencies up to 8 kHz. The possibility of operating the device in a self-oscillating mode at frequencies of the order of 100 kHz is demonstrated.     

Catalytic hydrochlorination of acetylene on mechanochemically-activated K<Subscript>2</Subscript>PdCl<Subscript>4</Subscript>

We report the catalysis of the hydrochlorination of acetylene on the surface of dry K₂PdCl₄ subjected to prior mechanical activation in an atmosphere of acetylene or propylene. The stereochemistry of the reaction corresponds to trans addition of the halogen and hydrogen atoms to the C-C triple bond. The hydrogen halide is the source of the halogen atom in the reaction product. The mechanical activation of K₂PdCl₄, in contrast to the case of K₂PtCl₄, is also capable of activating the C-C double bond: propylene is hydrochlorinated under similar conditions to isopropyl chloride. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 5, pp. 306–309, September–October, 2008.     

Use of local search in the metric traveling salesman problem

The traveling salesman problem (TSP) for points in the Euclidean plane is considered. For several approximation algorithms, such as the tree algorithm and algorithms based on matching, a local search method using permutation in groups of closely placed points in a route is applied. Some modifications of these algorithms are presented. The effect of applying the local search method for partially constructed routes is examined for the modifications. In this paper, experimental results from statistical modeling with randomly equidistributed points are discussed. It allows one to conclude on the advantage of one or the other algorithms. Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 129–134, March, 1999     

Influence of the “intrinsic” effect of the field on the thermally stimulated conductivity of ferroelectrics-semiconductors

Based on investigations of thermally stimulated conduction (TSC) in Sn₂P₂S₆ single crystals and the effect of the surrounding gas on the character of the thermally stimulated current, it is concluded that the degree of unipolarity of ferroelectrics-semiconductors and the screening conditions play a significant and sometimes determining role in the filling of local levels, manifested in the TSC curves. By combining the standard method of TSC with the method of TSC in the photoelectret regime based on the intrinsic effect of the field, it is possible to distinguish the surface and volume attachment levels. The greatest filling of surface levels at the ends of domains is obtained from TSC curves measured in a vacuum on single-domain samples with the pulling field oriented in the same direction as the internal field and the greatest filling of volume levels is obtained with minimum unipolarity of the crystal and the creation of depleted layers on its free surface by adsorption.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 86–90, March, 1990.     

Ab initio theory of many-body interaction and cauchy relations in compressed rare-gas crystals

The short-range many-body forces induced by the overlap of electron shells of atoms have been investigated. The nonorthogonality of atomic orbitals of the nearest neighbor atoms of a crystal leads to the appearance of terms in the potential energy, which depend on the coordinates of three, four, and more nearest neighbor atoms. An expression has been obtained for the energy of the electron subsystem of the crystal in the Hartree-Fock approximation in the basis set of atomic orbitals exactly orthogonalized at different crystal sites. The behavior of the contributions from two-particle, three-particle, and many-body interactions to the crystal energy under compression has been analyzed. The short-range three-particle potential has been calculated from first principles and proposed in the simple form. The three-particle forces obtained change the behavior of the dispersion curves for all wave vectors, in particular, thus violating the Cauchy relation. The theoretical and experimental deviations from the Cauchy relation for argon are in good agreement over a wide pressure range.     

The mechanism of formation and some properties of thin fluorocarbon films deposited onto silicon plates by electron-beam polymerization of hexafluoropropylene from the vapor phase

The results of studying thin fluorocarbon films deposited onto single-crystal silicon plates through electron beam polymerization of hexafluoropropylene from the vapor phase are presented. The films are deposited under the action of an electron beam with an energy of 40 keV at a monomer vapor pressure of 5- 20 hPa. It is shown that plastic solid films consisting of a low-molecular-mass polymer with low thermal stability are formed at a beam current density on the order of 20 μA/cm², while at current densities on the order of 150 μA/cm², rigid brittle films of three-dimensional crossl inked polymer are formed with a thermal stability of about 350°C. It is assumed that the films are formed via chain polymerization, which at high current densities, is accompanied by polyrecombination processes leading to efficient chain crosslinking. It is found that polymer clusters are ordered in the course of film formation.