R. C. Mowrey

Chemical forces associated with deuterium confinement in palladium

First-principles and empirical methods are used to study the effective interaction between two deuterons in a palladium lattice. No effects are found to suggest confinement of deuterons at distances much smaller than the gas-phase D2 separation.

Limits of chemical effects on cold fusion

Cold fusion enhanced by chemical confinement of deuterons has been suggested as an explanation of recent reports of the production of neutrons in electrochemically-generated palladium deuterides. To test this suggestion local-density-functional cluster calculations were used to study the coulomb barrier between two deuterons within the octahedral cage in crystalline palladium. The calculated repulsive forces were always greater than the corresponding forces between deuterons in molecular D2. These results imply that the room temperature fusion rate at this site is negligible.

Relative Energetics of C 44 Fullerene Isomers

We have carried out an exhaustive search of the energetics of all 87 isomers of the fullerene C44 using an empirical potential function. We find no single structural isomer with exceptional stability, suggesting that the enhanced abundance of this cluster observed in some studies may be due to a mixture of different molecules. We find in general that smaller, more spherical clusters and clusters whose pentagons are more isolated tend to be more stable, although the energy differences are not sufficiently large with our classical potential function to identify a particular criterion that distinguishes the stability of various similar isomers.

D-D (H-H) Interactions within the Interstices of Pd

Embedded atom, local-density-functional, and Hartree-Fock methods are used to calculate the effective interaction between deuterium (or equivalently within the Born-Oppenheimer approximation hydrogen) nuclei within palladium. No effects were found to suggest that the repulsion between deuterons in gas phase D2 is reduced within the octahedral and tetrahedral interstices of this transition metal.

Virtual Symmetric Charge Transfer Superconducting Pairing Excitations in C60

The recent discovery of superconductivity in the alkali-fullerides has focused intense interest on the origin of the superconductivity in these new cluster materials. These materials’ narrow conduction bands, short coherence lengths, and unusually high T c ’s suggest that electron-electron interactions are potentially important in explaining their superconductivity. We have examined the character of the lowest energy, most retarded, virtual charge transfer excitations of a single C60 molecule. We find that these excitations produce identical intermediate polarizations on opposite sides of the C60 molecule leading to a pairing interaction that operates across the equatorial plane of the C60 molecule. These excitations arise from local field effects and, in contrast to more usual dynamic polarization mechanisms, are not dipole active. To the extent that this mechanism proves important, it begins to provide a cogent framework for the design of other cluster- and molecular-based superconductors.

Molecular-Dynamics Simulations of C 60 /He Collisions

It has been reported[1] that collisions between C 60 + and He with energies in the tens of electron volts in the center-of-mass reference frame produce not only the expected smaller fullerene fragments but also many of their He adducts. More recently, C60He+ has been observed as a collision product[2] and some evidence indicates that the He atom resides within the fullerene cage. We have performed molecular dynamics simulations for collisions between C60 and He with the goal of studying the details of the trapping process. Direct scattering from the outside of the cluster, transmission through the cluster, and trapping of the He atom within the cluster were observed. Relative abundances of C60He+ are calculated as a function of the collision energy and are compared with experimental measurements.