Effect Of Intermolecular Forces Research Articles

The effect of intermolecular interaction on the asymmetry stretching vibration of CS 2

A quantitative interpretation of the 13C/ 12C vapor pressure isotope effect (VPIE) in CS 2 indicates that the frequency shift on condensation in the asymmetric stretching mode, υ 3, to be ascribed to the effect of intermolecular forces is 13 ±3 cm −1. When combined with the spectroscopically observed shift, 27cm −1, a soundly based value for the “dielectric correction” for this absorption band is obtained. The result is of interest, and indicates that thermodynamic data on isotope effects can be used to test this aspect of spectroscopic theory.

A nonlocal continuum theory for diatomic elastic solids

In this study, taking the effects of long range intermolecular forces into account, a mechanical model for diatomic solids is presented. The model we use is based upon the assumption that a diatomic solid may be considered to consist of two simple elastically interacting media which are initially overlapping but may have relative motions at a later time t. Based on this assumption, the kinematics and balance laws, i.e. conservation of mass, balance of momenta, conservation of energy and equation of entropy production are presented. The nonlinear and linear constitutive equations and the discussion of some special cases are introduced in Sections 3 and 4, respectively. To illustrate the theory, in the final part, the propagation of time harmonic waves in such a medium is studied, and by comparing present result with those of lattice dynamics, the explicit form of influence functions is obtained.

Effect of intermolecular and electrostatic cohesive forces on the process of densification of particulate materials

Effect of intermolecular and electrostatic cohesive forces on the process of densification of particulate materials

A modified hard-sphere theory for transport properties of fluids over the whole density range: I. Viscosity coefficients of low molecular weight hydrocarbons

The rough hard-sphere model is used as a basis for the interpretation of viscosity coefficient data for liquid methane. It is found that effects of coupling of translational and rotational motions are absent and that the molecules behave like an assembly of smooth hard-spheres rather than rough hard-spheres. The effect of non-spherical molecular shape on the viscosity coefficient of C 2 to C 5 hydrocarbons at high density is investigated. Other work has shown that for a dilute assembly of spherocylinders the viscosty coefficient can have practically the same value as a hard-sphere gas with the same molecular volume. The hard-sphere theory is here applied to liquid hydrocarbon viscosity coefficient data and to the dense gas data and the results show that at these densities also the experimental data can be satisfactorily interpreted in terms of the smooth hard-sphere model. At lower densities the experimental results are lower than values calculated on the basis of the smooth hard-sphere theory, a consequence of the effect of intermolecular attractive forces in real fluids. These effects are taken into account by an empirical modification to the hard-sphere theory. The resulting expressions reproduce the experimental viscosity coefficient data for the C 1-C 5 hydrocarbons considered very satisfactorily over the whole density and temperature range.

Molecular theory of optical polarization and light scattering in dielectric fluids. I. Formal theory

A molecular theory, based on first principles, is introduced for the systematic study of the effects of intermolecular forces on optical properties of dielectric molecular fluids. This theory covers a broad range of applications, including (polarized and depolarized) Rayleigh and Raman scattering, absorption spectra, and nonlinear optics. A canonical transformation is presented by which externally applied coherent fields can be separated from internal radiation fields, thus enabling the introduction of radiative corrections (such as retardation) to the intermolecular forces. The polarization of the medium is expressed in terms of a manybody polarizability (or nonlocal susceptibility) operator. The latter quantity contains implicitly all so-called local-field effects (modification of the molecular polarizability by electromagnetic fields due to neighboring molecules). The dipolar contributions, when summed to all orders, yield the familiar Lorentz-Kirkwood factor, involving the retarded dipole tensor.

Molecular theory of optical polarization and light scattering in dielectric fluids. II. Extensions and applications

A microscopic theory of light scattering developed in a previous publication, which incorporates all intermolecular-force effects, is here extended and applied to specific experimental situations. The consistency between the molecular theory and macroscopic theories of light scattering is established. The formal theory is then elaborated to include explicitly the contributions of higher-multipole hyperpolarizabilities, and of nonlinear effects of the external field. The many-body hyperpolarizabilities are expanded in terms of the corresponding single-particle operators and intermolecular forces. Three specific applications of this formalism are considered: (a) collision-induced forbidden Raman scattering in which higher-multipole polarizabilities are shown to partake; (b) collision-induced second-harmonic generation (SHG) by fluids of centrosymmetric molecules; and (c) SHG by atomic fluids. The latter process is shown to contain direct information on the three-particle correlation function.

Theory of surface tension for molecular liquids. II. Perturbation theory calculations

A general perturbation expansion for the surface tension of a molecular liquid is considered, and the first order term is evaluated. For the special case of a Pople reference potential, perturbation terms up to the third are evaluated for both the general interface and for the Fowler model (abrupt vapor–liquid transition). A Padé approximant to this latter series, similar to that used by Stell, Rasaiah, and Narang for the free energy, is proposed and is used to calculate the effects of dipolar and quadrupolar intermolecular forces on the surface tension. The effects of anisotropic overlap and dispersion forces are also computed, using the series terminated at the second order term. The Padé approximant is also compared with experimental data for hydrogen bromide; using the Fowler approximation, good results are obtained for the low temperature liquid.

A modified hard-sphere theory for transport properties of fluids over the whole density range: II. Viscosity coefficients of diatomic molecules F2 and O2

Viscosity coefficient data for the diatomic fluids fluorine and oxygen are very satisfactorily interpreted on the basis of a modified smooth hard-sphere model. The effect of intermolecular attractive forces on the viscosity coefficient at low densities is found to be similar to that previously found for low molecular weight hydrocarbons.

Excess thermodynamic properties for liquid mixtures of non-spherical molecules

Perturbation theory is used to estimate the effect of anisotropic intermolecular forces on excess thermodynamic properties in liquid mixtures. Using a mixture of argon and krypton at 115·8 K as the reference system, the effects of adding point dipole, quadrupole, octopole, and anisotropic overlap potentials are calculated. These forces cause G E, V E, S E and H E to increase. The effect on S E and C V E is particularly noticeable. S E changes sign in many cases; for certain (fixed) values of the anisotropic strength parameters the sign of S E changes with composition. Comparisons of theory and experiment are reported for the systems Ar + N2, Ar + CH4, and CH4 + CF4.

Thermodynamics of Poly(dimethylsiloxane) Solutions. Combinatorial Entropy and Molecular Interactions

AbstractGas‐liquid chromatography (glc) was used to measure activity coefficients of 22 solvents at infinite dilution in poly(dimethylsiloxane) in the temperature range 2570 °C. Flory χ parameters from glc are close to, but generally a little lower than, those extrapolated to infinite dilution from static measurements at finite solvent concentrations.The new measurements, coupled with previously published heat‐of‐mixing data and with volumetric data for the pure components, were used to establish an empirical test of the Flory‐Huggins approximation for the combinatorial entropy of mixing. In this test, the effect of intermolecular forces on solvent activity is obtained from heats of mixing and the effect of differences in free volume is calculated from an equation of state. The test indicates that errors in this approximation are sufficiently large to account for apparent inconsistencies when all the data for a binary system are examined simultaneously. These inconsistencies can be eliminated if the Flory‐Huggins entropy formula is replaced by an exteneded combinatorial formula which takes into account differences in molecular size and shape between polymer segments and solvent molecules.

The role of molecular forces in the scavenging of aerosol particles.

Abstract The effects of intermolecular forces on the collection efficiency of submicron aerosol particles are studied. It is assumed that the intermolecular forces provide a certain region as an absorbent surface in the vicinity of the drop. Numerical results have been obtained for the cases of a water drop collecting AgCl aerosols and a water drop collecting submicron cloud droplets. It is found that the collection efficiency depends mainly on the diffusion process. Our calculations agree reasonably well with recent experimental results of Kerker for AgCl aerosols for the case of small drop.

Low frequency Raman spectra of hexamethylbenzene crystal

AbstractLow frequency Raman spectra (below 200 cm −1) of hexamethylbenzene and hexamethylbenzene‐d18 were measured in all the crystalline phases. (I, II, and III) and in the liquid phase. Two bands were observed in each crystalline phase. Vibrational analysis was done on the basis of deuteration effect and polarized Raman spectra of single crystal, effect of intermolecular forces was also considered. The nature of the low frequency vibrations is discussed in each phase.

Dielectric relaxation in styrene‐related polymers at low temperatures

AbstractThe complex dielectric constants ϵ* = ϵ′ − jϵ″ of each of several members of a system of copolymers of 4‐chlorostyrene and 4‐methylstyrene have been measured from 1.6°K to 300°K and from 0.1 kHz to 20 kHz. The principal experimental findings are: the strength of the relaxation process which occurs near 50°K at 1 kHz varies linearly with changing copolymer composition; both the apparent activation energy (H = 2.7 ± 0.7 kcal/mole) and the shape of the relaxation curve are independent of the composition variable and of the temperature (or frequency) within the ranges studied; and the ratio of the relaxation strength of poly‐4‐methylstyrene to that of poly‐4‐chlorostyrene in the 50°K process is about 25 times the corresponding ratio for the primary relaxation process that occurs in the neighborhood of the glass‐transition temperature. These findings suggest that in the 50°K process the phenyl groups relax independently of one another; that the apparent activation energy and the shape of the relaxation spectrum are determined primarily by the nature of the intrachain forces; and that the strength of the relaxation process depends primarily on effects of intermolecular forces that are governed by the molar “free volume” of the copolymers.

Effect of Intermolecular Forces on the Annihilation of Positrons in a Nematic Liquid Crystal

Lifetime spectra have been measured for positrons annihilating in the liquid-crystal $p$-azoxyanisole. Four lifetime components appear when positrons annihilate in either the nematic mesophase or in the isotropic liquid phase, but in solid $p$-azoxyanisole the longest-lived component is absent. No abrupt changes in either lifetimes or intensities are observed across the nematic-isotropic transition; however, the solid-nematic transition produces changes in all annihilation parameters which are unattributable to the accompanying 0.1% density change. Annihilation mechanisms are proposed to account for the observed positron lifetime components and their dependence on phase. The degree of molecular orientation appears to have little direct influence on annihilation behavior, but the nature and strength of the intermolecular forces in different phases can greatly affect the positron lifetimes and intensities.

Etude Experimentale De L'elargissement Par La Pression Des Raies De Rotation Du Spectre Raman De L'acide Chlorhydrique

Widths of the pure rotational Raman lines of HCl were measured for several pressures in the range 1–35 bar. A self-broadening coefficient showing a dependence on the rotational quantum number J was derived. Its variation with J agrees with Gray's theoretical predictions based on anisotropic intermolecular force effects.

A Semi-theoretical van der Waals Equation for Calculation of Vapor-Liquid Equilibria at High Pressures

An equation of the van der Waals type is derived and applied to the calculation of vapor–liquid equilibria at elevated pressures. For the hard-sphere part of the equation the theoretical relation of Carnahan–Starling is used. The effect of intermolecular forces is represented by the usual van der Waals term but the "constant a" is permitted to vary with temperature and density as dictated by the experimental PVT data for argon; this variation of the "constant a" is generalized for other simple fluids through corresponding states. While this treatment is of little interest for representing the configurational properties of pure fluids, it is useful for calculating the properties of simple fluid mixtures. Illustrative vapor–liquid equilibrium calculations are performed for binary and ternary mixtures of nitrogen, argon, and oxygen at 6 and 18 atm.

Effect of Concentration and Intermolecular Forces on the Sedimentation of Polystyrene Spheres

At low concentration, the sedimentation coefficient s can be related to the sedimentation coefficient at zero concentration s0 through a power series expansion in the volume fraction Φ, i.e., s = s0(1 + KΦ···). We discuss the calculation of the constant K for sedimenting charged spheres. The spheres interact hydrodynamically as well as through a potential consisting of a hard-core repulsion, a screened Coulomb repulsion, and a London–van der Waals attraction. To calculate K one must know the value of the electrostatic potential in the vicinity of the surface of the sedimenting sphere ψδ, and the Hamaker constant, the constant which measures the strength of the London–van der Waals attraction. It is shown that knowledge of any two of the three quantities K, ψδ, and the Hamaker constant allows one to find the third. It is also shown that if both ψδ and the Hamaker constant are unknown the experimental determination of K can be used to obtain upper and lower bounds on the Hamaker constant. Using Cheng and Schachman's experimental value of K for polystyrene latex spheres, the following bounds for the Hamaker constant for polystyrene in aqueous solution are found: 3–8 × 10−14 erg. These bounds are in good agreement with previous experimental determinations.

Osmotic Pressures of Polystyrene, Poly-p-chlorostyrene and Poly-o-chlorostyrene Solutions

Abstract Second virial coefficients for polystyrene (PS), poly-p-chlorostyrene (PPCS), and poly-o-chlorostyrene (POCS) were determined in various solvents by osmotic-pressure measurements. Free-energy parameters, χ, were estimated from the values of the second virial coefficients. It was shown that the values of χ in each solvent at 30°C became larger in the following order: PS, POCS, PPCS in toluene; PS, PPCS, POCS in chlorobenzene; PPCS, PS, POCS in n-butyl acetate. It was indicated that, in addition to the effect of intermolecular forces, another parameter related to the stiffness of the polymer chains should be considered in order to discuss the thermodynamic properties of polymer solutions. It was shown that the values of χ for two polychlorostyrenes in n-butyl acetate increased with an increase in the temperatures, unlike the behavior of PS in the same solvent.

Effect of dipole-dipole intermolecular forces on the vibrational spectra of organic compounds

Effect of dipole-dipole intermolecular forces on the vibrational spectra of organic compounds

Effects of dipole-dipole intermolecular forces on the vibrational spectra of organic compounds

Effects of dipole-dipole intermolecular forces on the vibrational spectra of organic compounds