Showing papers on "Chemical binding published in 1985"

On the role of Gibbsian segregation in causing preferential sputtering

Abstract: It is well known that preferential sputtering with binary alloys correlates significantly with chemical binding, but only the sense and not the magnitude of the effect can be understood in these terms. It is argued here that the correlation is, in fact, an indirect one due to bombardment-induced Gibbsian (or similar) segregation. The preferentially removed component is characterized by a composition profile consisting of a one atom-layer-thick spike at the surface; this is the depth from which most sputtered atoms originated so the spike must have near-bulk composition. There is then a severely depleted subsurface region in accordance with Gibbsian segregation equilibrium (or an equivalent effect) and a final return to bulk composition. The reason for the marked correlation with chemical binding is that segregation is governed significantly more often by binding than by the alternatives of size, surface chemistry, an interstitial flux, or long-range ordering.

Lipid derivatives, their production and use

Abstract: Novel lipid derivatives of the formula ##STR1## [wherein R1 is alkyl or alkylcarbamoyl; R2 is hydrogen, hydroxy which may be substituted, amino which may be substituted or cyclic amino; R3 is a chemical binding or alkylene which may be substituted; R4 is hydrogen, alkyl or aralkyl; X and Y are independently O, S or an imino group which may be substituted, and when Y is an imino group, Y, together with the imino group represented by X or R4, may form a ring; and Z is imino or a nitrogen-containing heterocyclic ring which may be substituted] and salts thereof have inhibiting activity on platelet activating factor and are useful as a preventive or therapeutic agent for a variety of circulatory diseases and allergic disorders and also as an antineoplastic agent.

Chemical binding and electron correlation in diatomic molecules as described by the FORS model and the FORS-IACC model

Abstract: Using the model of the Full Optimized Reaction Space including the Intra-Atomic Correlation Correction, binding energies and other electronic properties have been calculated for several states of a number of diatomic molecules. In most cases this theoretical approach yields results agreeing with experimental values to within 0.2 eV. The investigation covers the molecules BH, CH, NH, OH, FH, N2, O2, F2.

On the effect of nuclear motion on chemical binding

Abstract: Extending the previous work of Berlin to the case where the atomic nuclei in molecules are moving, we obtain a generalized equation for the ‘‘surface of Berlin’’ starting from the hypervirial theorem. We apply our result to the hydrogen molecule in its ground state and show that the corresponding surface is different from the one obtained by Berlin for the case of fixed nuclei, because now it encloses a finite region of space, in which electrons contribute to the binding.

An investigation of the logarithmic mean excitation energy for the stopping power of molecular hydrogen

Abstract: An examination is made of reported experimental and theoretical values of the logarithmic mean excitation energy, l, for the stopping power of molecular hydrogen and of values of l determined in this work from various recent experimental values of the stopping cross-section of molecular hydrogen for α-particles and protons of various kinetic energies. Values of l for molecular hydrogen determined in this work from experimental values of the stopping cross-section reported recently by various investigators give support to a value of over 20 eV for l of molecular hydrogen that was predicted by a recent application of the local plasma model for the determination of l that took chemical binding into consideration. This value is much higher than all of the previously accepted values of l for molecular hydrogen.

Applications of Solid-State Magic Angle NMR Spectroscopy to Fiber Reinforced Composites

Abstract: The solid-state NMR techniques of cross polarization (CP), high power proton decoupling and magic angle sample spinning allow one to study the binding of coupling agents to silica surfaces, γ-mercaptopropyltrimethoxysilane (y -MPTS), γ-aminopropyltriethoxy-silane (γ-APS), γ-glycidoxypropyltrimethoxysilane (γ-GPS), γ-metha-cryloxypropyltrimethoxysilane (γ-MPS) and vinyltriethoxysilane (VTES) were the organosilanes utilized on high-surface-area silica. High resolution solid-state 13C NMR spectra were obtained for coupling agents adsorbed on silica surfaces and for the corresponding coupling agents condensed as bulk polymers. Chemical shifts and line widths of the resonances of the chemically modified silicas are compared to those resonances arising from the bulk organosilanes. The spectra confirm chemical binding of the coupling agent to the silica surface. A graphite-filled epoxy is characterized in terms of molecular motion. In this study 13C spin-lattice relaxation times in the rotating frame of reference (T1ρ) were obtained for the composite.

Valence Force Constants of Carbonyl Bonds in Naphthaldehydic Compounds as Chemical Binding Correlation Parameters

Abstract: T h e relative stabilities of various conformat ions of subst i tuted naphthalenes and a romat i c aldehydes have been deduced f rom several semiempir ical and exper imenta l methods [1-5] . However , to our knowledge, normal coordinate analysis, or the characterizat ion of the vibrational potential function of these large molecules, have not been published up to now. In order to analyze the substituent effect on the carbonyl bond in naphthaldehydic compounds , we have used a point-charge model developed by Kosmus [6]. The valence force constants of the carbonyl bond are studied by means of the substituent effect across the aromatic system. T h e Kosmus formula t ion , a s imple method to discuss bond propert ies at the equi l ibr ium position, allows us to est imate the electronic contr ibut ions to the force constants. These valence force constants calculated f rom computat ional C N D O / 2 data have been shown to be appropr ia te to describe various molecular systems [7], T h e valence force constants, / ( O C ) , of a bond O C according to Kosmus's work (6) is given by the equat ion

Coupling agent between mineral fillers and polymers

Abstract: New coupling agent between mineral fillers on one hand, particularly CaCO3, and polymers on the other hand, intermediary products for producing said coupling agents, process for producing the intermediary products, mineral fillers and process for producing said mineral fillers. The new coupling agents are characterized by the general formula Y - R - X, wherein X is one or a plurality of acid groups for the alkaline or alkaline earth sort(s), Y is one or a plurality of reactant groups pertaining to the class of organic acids as nitrene source and R represents a chemical binding part between the two reactant groups X and Y in the form of an aliphatic and/or olefinic and/or aromatic intermediary element comprising from 2 - 40 atoms of carbon. Particularly useful properties are the attribute of coupling agents of the group of azidosulfonyl carbonic acids having the general formula N3SO2-A-Z-B-COH, wherein A and B are aliphatic and/or aromatic rests comprising each from 2 to 18 atoms of carbon and Z is O, S, or N.

Bremsstrahlung isochromats from transition metal carbides: The cubic mono-carbides TiC, ZrC, HfC, VC, NbC, TaC

Abstract: Bremsstrahlung isochromats of polycrystalline TiC, ZrC, HfC, VC, NbC, and TaC have been measured at a monochromator energy of 1,008.2 eV. The curves are similar to those of the pure metals, but show a secondary structure caused by the chemical binding of metal and carbon. The experimental results are compared with density-of-states calculations. Together with XPS-measurements, they allow to derive the widths of the total conduction bands of the carbides, which are compared with thed-band widths of the pure metals and with band structure calculations.