Dipole-type Interactions Research Articles

A model of quantum scalar dipole-type X-exotic-boson field at finite temperature

We examine an arbitrary order dimension system of two scalar neutral fields by means of a 1/N expansion method. Using the partial normal-ordering procedure, an application in the study of a light scalar dipole-type field interaction with quarks is proposed. A hypothetical candidate for a (pseudo)-scalar coupling between the quarks inside the bound system would be a light Higgs-like exotic X-particle. The derivative relation of the physical neutral scalar field mass with respect to non-zero temperature is illustrated.

On the correlation between the retention volume of selected compounds and the surface free energy of controlled porosity glasses

The retention volumes of cyclohexane, n-octane, benzene, toluene and ethylbenzene were correlated with the surface free energy of controlled porosity glasses. Linear relationships were found between the retention volume and the film pressure of the adsorbate (corrected with respect to its saturated vapour pressure) and between the natural logarithm of the retention volume and the total surface free energy. The retention volume of saturated chain hydrocarbon (n-octane) did not fit the above-mentioned relationships. This was attributed to dispersive interactions only between surface and n-octane molecules, when compared to benzene homologues. The contribution of dipole-type interactions to the total energy of interactions was found to be ∼20%, when compared to those of π-electrons. The mechanism of n-octane retention which is different from that of benzene homologues presented certain difficulties in the separation of n-octane from benzene and toluene, depending on the magnitude of the specific surface interactions of the investigated controlled porosity glass.

Molecular dynamics simulation for an ensemble of coupled quantum two level systems with classical degrees of freedom

An ensemble of model particles represented as quantum two level systems with induced dipole–dipole-type interactions is studied with molecular dynamics techniques. The particles are treated as oriented molecules according to the direction of the actual dipole moment. A set of equations of motion is derived on the basis of a time-dependent Hartree method, considering the classical limit for the rotational motion. From the numerical calculations, three different types of behavior for the ensemble of model particles are found. For weak interactions the system nearly behaves like an ensemble of uncoupled particles. With increasing interaction strength, the intramolecular energy starts to oscillate between the two levels, while in the strong interaction range the quantum states of individual molecules are represented by stationary linear combinations of the two states of the model quantum system for the particles. The change in behavior, when going from medium to strong interaction, occurs like a phase transition in bulk matter. The simple model presented here is well suited to describe the generic properties of an ensemble of molecules which may perform an intramolecular rearrangement which is essentially quantum mechanical. Similarities of the model system to a set of ammonia molecules (with the well-known inversion) are pointed out.

Microscopic theory of quantum fluid at nonzero temperature. The momentum distribution, liquid-structure factor and ground-state energy of liquid4He

Employing theU-matrix theory in the present form we have presented a microscopic theory of an interactingN-boson system at nonzero temperature. The Hamiltonian includes a term describing the external influence, a term for a two-particle interaction and one pertaining to the dipole-type interaction. To study the ground state of liquid4He, only the two-particle interaction is included. Based on scattering data, we have deduced the two-particle potential function. With that we calculate numerically the momentum atT=1.1 K for several sets of parameters. It is shown that the theoretical curves agree well with the observed results. The corresponding liquid-structure-factor curves fit the measured data very well and the best result for the ground-state energy is −7.12K.

An extended version of Boyd's force field method applicable to heteroatomic molecules: Part 1. Adenine and uracil

The force field method developed by Boyd is extended to include molecules containing atoms other than C and H (e.g., N, O, P, S, Cl, Br, …). A new set of force field parameters is determined in order to redefine the potential energy functions that govern the dynamics of the internal (valence coordinates) degrees of freedom of a molecule. It is shown that the minimum of the partial potential energy surface is significantly affected by electrostatic intramolecular interactions. In this regard the non-bonded interactions appear to be less important than the dipole—dipole type interactions for a given interatomic distance when heteroatoms are present in the molecular framework. The reliability of the extended method as regards minimized structure, vibrational spectra and thermodynamic properties has been checked for more than 20 polyatomic molecules. From the correlation between calculated and experimental properties it is concluded that the method has good potential for further applications on polyatomic molecules with increasing size and topological compexities such as adenine and uracil.