[en] In studying the ''internal'' motions of a molecule (a many-particle system), use has been made of the Eckart frame, relative to which the molecule moves without rotation. This paper shows, on the geometry of the center-of-mass system due to A. Guichardet, that the Eckart frame exists for any configuration of the non-rigid molecule, but not uniquely. The main purpose of this article is then to apply the reduction method of Marsden-Weinstein to the Hamiltonian system which describes the classical molecular dynamics and is defined on the cotangent bundle of the center-of-mass system, in order to eliminate the rotation motion. If the angular momentum is not zero, nor the molecule is restricted on a fixed plane, the reduced phase space is larger than the cotangent bundle of the internal space and carries the two-form to which the source of the Coriolis force is attributed

[en] We report additional results on a simple model of polymers, namely the diffusion in concentrated polymer systems and the static properties of one long chain in a dilute melt of shorter chains. It is found, for the polymer sizes and time scales amenable to our computer calculations, that there is as yet no evidence for a ''reptation'' regime in a melt. There is some indication of reptation in the case of a single chain moving through fixed obstacles. No statistically significant effect of the change, from excluded volume behavior of the long chain to ideal behavior as the shorter chains grow, is observed

[en] We try to suggest that the threshold effects and the rotational-like behaviour of the resonances masses seems to hide a common molecular picture for the low mass dibaryon resonances. (author)

No abstract available

[en] A major advantage of the use of floating spherical Gaussian or vitals (FSGO) is the extreme rapidity with which the necessary quantum mechanical integrals can be evaluated. This advantage has been exploited in several quantum mechanical procedures for molecular electronic structure calculations, as described below. Several other properties of these functions have also been exploited, and have led to the development of semiclassical point charge and harmonic oscillator models capable of describing first and second order electromagnetic properties and intermolecular forces with reasonable accuracy in all cases and with considerably better accuracy than much more elaborate theoretical procedures in some cases. These applications are also described below. The primary intent of the current paper is to present an overview of some of the uses of FSGOs in the study of molecular electronic structure and properties and to indicate possible directions for future applications. No attempt will be made to include all possible applications. Rather, those applications of interest to the authors have been stressed. Hopefully, this paper will further stimulate the development of additional uses of these remarkable functions

[en] We describe the results of computer simulations on a model polymer chain with excluded volume interactions in the presence of an external stretching force. For weak and moderate forces the response is linear while for strong forces the behavior is nonlinear, consistent with the non-Gaussian nature of the end-to-end vector R distribution for large R. In the vicinity of the THETA temperature the onset of nonlinearity occurs at larger forces

[en] Molecular dynamics simulations of carbon cluster nucleation was conducted using a modified form of the Chelikowsky interatomic potential. The simulations were performed for systems containing 40 to 80 carbon atoms using annealing procedures which are more physically realistic than those used in the past. The results show that at temperatures above melting, long linear chains form early in the nucleation process and subsequently close to form monocyclic rings. Once the temperature is decreased below the melting point the network of rings closes forming hollow spheroidal structures characteristic of the fullernes. The pattern of growth results confirm predicted growth processes, indicating the advantages of Hamiltonian dynamics over previously used Langevin dynamics

[en] The kinetics of excitation transfer between moving donors and acceptors in fluid solution is studied with a particular emphasis to the respective influence of the diffusive motion of the particules and of the mechanism of the reactive step. Our results show that all the microscopic properties of the transfer interaction (range and intensity) are included in the observable expressions of the transfer kinetics, in contrast to the conclusions of the widely used diffusion-limited reaction theory where the reactive interaction is represented by a more or less absorbing sink of arbitrary radius

[en] CNDO (Complete neglect of differential overlap) calculations are reported for a model of interstitial C and C₂ species between graphite planes, modelled by two C₁₆H₁₀ graphite like molecules. For a single C atom interstitial the optimum position is about 0.82 A above the centre of a ring. The interstitial is bonded to one plane with only a weak interaction with the plane above. For the C₂ interstitial, the optimum position is with each C atom 0.83 A above the ring in adjacent layers. Agreement with experimental values for the migration energy of an interstitial is not found, and may be achieved if deformation of the graphite layers is also taken into account. (author)

[en] Using thermo field dynamics, the authors investigate the symmetry behavior at finite temperature in an exactly solvable supersymmetric quantum mechanical model