VAN DER WAALS FORCES IN MANY-BODY SYSTEMS

Thesis/Dissertation · Mon Jan 01 04:00:00 EST 1962

OSTI ID:4695610

Yaris, R

In order to understand more fully the operation, in a many-body environment, of the familiar dispersion type attractive forces, theoretical investigations were conducted on three many-body systems. In all cases a variational form of perturbation theory was used, rather than the more usual Schroedinger form of perturbation theory. There is a quantum mechanical treatment of the physical adsorption of isotopic species. The seemingly anomalous experimental results of Constabaris, Sams, and Halsey, that D/sub 2/ interacts more strongly with a carbon surface than H/sub 2/ but CH/sub 4/ interacts more strongly than CD/sub 4/, is explained in terms of two competing effects: the quantum statistical mass effect on the vibrational energies normal to the surface, and the quantum mechanical effect of isotopic substitution on the dispersion energy. There is a treatment of the effect of three-body dispersion forces on physically adsorbed monoiayers. In this treatment a variational derivation of the three-body dispersion energy is presented and applied to the problem of two molecules interacting with a surface. The resulting equation, containing only experimentally measurable quantities, was compared with adsorption data of Ar, Xe, and CCl/sub 4/ adsorbed on P33 graphitized carbon black treated as a two-dimensional gas. It was concluded that the experimental data can be adequately explained by renormalizing the gas parameters for threebody dispersion effects, and that it is not necessary to postuiate an electrostatic surface field. The polarizability change in iiquids due to many- body interactions is considered. Approximate quantum mechanical expressions were derived for the change of polarizability for a spherically symmetric liquid. These expressions are evaluated using Linder's continuum model for the liquid and Slater Type Orbital wave functions. It is shown that the change in polarizability is approximately (3/8)g alpha /sup 2/, where alpha is the unperturbed, isolated molecule, polarizability and g is a parameter which depends on the dielectric constant and molar volume of the liquid. The predicted increase in the polarizability due to many-body interactions is less than 7% for all molecules studied. (Dissertation Abstr. 23: May 1963)

• Research Organization: Originating Research Org. not identified
• NSA Number: NSA-17-026251
• OSTI ID: 4695610
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ADSORPTION
ARGON
BINDING ENERGY
CARBON
DEUTERONS
DIELECTRICS
DISPERSION THEORY
ELECTRIC FIELDS
ELECTROSTATICS
ENERGY LEVELS
ENVIRONMENT
EQUATIONS
GASES
GRAPHITE
HYDROGEN
INTERACTIONS
ISOTOPES
LAYERS
LIQUIDS
MANY BODY PROBLEM
MASS
METHANE
MOLECULES
OPERATION
PERTURBATION THEORY
PHYSICS
POLARIZATION
QUANTUM MECHANICS
SCHROEDINGER EQUATION
STATISTICS
SURFACES
VAN DER WAALS FORCES
VIBRATIONS
VOLUME
XENON