Next-neighbor Interactions Research Articles

Dynamics of diluted antiferromagnetic Ising spin systems on the fcc lattice.

We consider Glauber dynamics of Ising spins randomly populating sites of the fcc lattice and coupled by nearest-neighbor antiferromagnetic interaction J. This investigation extends our former studies of small clusters beyond the percolation threshold and is aimed at modeling semimagnetic semiconductors. The energy barriers against inversion of local energy minima are found to be integer multiples of 2\ensuremath{\Vert}J\ensuremath{\Vert}. If small next-neighbor interactions, ${J}_{\mathrm{NN}}$, are taken into account, the distribution of the barriers remains peaked at these values. The spectrum of relaxation times may then contain gaps at low temperatures, depending on relative strength of ${J}_{\mathrm{NN}}$ to J. We have studied dynamics of the system for ${J}_{\mathrm{NN}}$=0 in Monte Carlo simulations. Decays of time delayed single- and two-spin correlations, above the critical temperature, are found to be consistent with that given by a sum of distinct exponential terms. We also studied the dynamic spin susceptibility by applying an oscillatory magnetic field and by monitoring oscillations in the induced magnetization for small frequencies \ensuremath{\omega}. The susceptibility is found to show structure as a function of log\ensuremath{\omega}.

Modular gating channel and Cole-Moore effect: next-neighbor (Hill-Chen) versus nonrestricted aggregation

When the principle of aggregation is applied to electrically gated channels, the fundamental differences between an aggregation process that is limited to next-neighbor interactions and one that is not can become decisive for the viability of an hypothesis. This is demonstrated for the case of the Cole-Moore criteria for induction and superposition.

Determination of the interface distribution function of lamellar two-phase systems

The concept of interface distribution functions [Ruland (1977). Colloid Polym. Sci. 255, 417–427] has been applied to the evaluation of the small-angle scattering of a series of polyethylene samples. The results indicate that the statistics of the lamellar stacking is not necessarily determined by next-neighbor interactions and that non-negligible volume fractions of amorphous domains outside the lamellar systems are observed in a number of samples.

Adsorption from aqueous and nonaqueous solutions on hydrophobic and hydrophilic high surface-area copolymers

The adsorption of fatty acids and phenols on high surface polymeric sorbents with polar surfaces has been examined. The results obtained from equilibrium experiments with acetic and butyric acids, phenol, and substituted phenols in aqueous, toluene, and hexane solutions show that the new polar polymeric sorbents have a considerable adsorption capacity in non-aqueous solvents. The shapes of the binding isotherms of substitued phenols from aqueous solution on a new high surface area (860 m2/gm) hydrophobic adsorbent suggest that a next-neighbor interaction exists between molecules bound on adjacent sites. The equation described by A. Fowler and E. A. Guggenheim, who considered such interactions, fits the experimental data.

The binding of phenols to hair: IV. The binding of 1,3-dihydroxy naphthalene (DHN) to hair

The absorption of 1,3-dihydroxy naphthalene (DHN) by hair has been studied. The shapes of the binding isotherms suggest that two types of DHN binding sites are present in hair and that a next-neighbor interaction exists between molecules bound on adjacent sites. The binding mechanism of DHN has been compared to that of resorcinol, and the influence of the polarity of these two molecules on the absorption process discussed.

Electronic conductivity in Molecular Crystals: An Alternative to the Bloch-Function Approach

Bloch functions are not good basis functions for molecular crystals in high electric fields. When the interaction with the electric field is large with respect to next-neighbor interactions, it is better to use wave-functions which are localized over molecular sites as basis functions. A treatment of electronic mobility and diffusion in molecular crystals using quantum mechanical transition probabilities between localized energy levels and considering only nearest-neighbor interactions is developed. The asymmetry of the potential function, caused by the electric field, and the conservation of energy during transport are considered. The mobility is found to be independent of temperature, and the diffusion constant proportional to temperature. The magnitude of the diffusion constant calculated from phonon-induced transitions is quite reasonable (4.6×10—3). Photon-induced transitions do not appear to be important.