Polysulfur Nitride—a One-Dimensional Chain with a Metallic Ground State

Abstract

There are three parameters in Eq. (2) which determine the behavior of the model and these can, within limits, be determined without reference to surface order. We took J 2 Mi as -0.2, quite close to the preferred value of -0.25 suggested in Ref. 7. To illustrate best the contrast between results from the bulk and from the surface, we adjusted J ± so that the calculated points for the bulk order parameter agree with experiment 4 up to the experimental transformation temperature. This gave J 1 /k = 23TK, a value about 7% higher than would have been obtained by the procedure of Ref. 7. Finally we let AE = 2.5^, corresponding to a constant average surface composition.In Fig. 4 we show the average of the order parameters for the two topmost Cu-Au layers, for the two boundary conditions of the surface model, together with the measured surface order and the calculated bulk order as a function of temperature. It appears from the figure that the difference between the observed behavior of the longrange order parameter at the surface and that in the bulk can be explained by a simple model involving only nearest-and next-nearest-neighbor interactions which are the same for both surface and bulk. Furthermore, it is evident from the analysis that consideration of a region of accommodation between surface and bulk is a necessary Considerable interest exists in examining the properties of both organic and inorganic structures which are highly anisotropic and can be visualized as containing one-dimensional chainsmetallic "spines"-surrounded by a matrix whose properties are highly important in determining the transport properties of that system. The or-feature of any model meant to describe the phenomenon of long-range order at a crystal surface.The temperature dependence of the electrical conductivity and Seebeck coefficient for the polymer chain system (SN) X has been measured along the chain axis from 4.2 to 300°K. The data show the system to be metallic over the entire temperature range studied, with a small conductivity maximum at ~33°K.

The (Non-)Local Density of States of Electronic Excitations in Organic Semiconductors

“…Unfortunately, W (1) and W (2) as written down above in terms of integrals over the continuous molecular wave function are not computationally accessible for the large systems of interest here. In the following, we will therefore describe approaches how these expressions can be reformulated in terms of distributed molecular/atomic multipoles and polarizabilities that allow us to compute these perturbative corrections efficiently in a classical expansion.…”

“…For illustration, Fig. 3.1a-c provides a summary of its convergence behaviour in different 3D-and 2D-periodic systems, indicating how the electrostatic contribution W (1) to the energies of different electronic states changes with the size of the molecular cluster d c on which computations are performed. For charges embedded in a 20 nm-thin film ( Fig.…”

“…In (c), the black curve denotes the convergence trend for an interfacial charge transfer state, broken down into the contributions of the CT hole (red curve) and CT electron (blue curve) in the same plot. Configuration energies W (1) for the infinite systems are shown on the very right of each plot, where for the bulk setup a macroscopically spherical shape has been chosen to remove the conditional convergence for the 3D-periodic case, which corresponds to the spherical shell-by-shell growth of the molecular cluster of size d c . The schematics on the right-hand side indicate the system under study including cartoons of the two molecular species (D5M and C 60 ), with a system repeat unit coloured in black, and periodicity indicated by dashed arrows.…”

“…For MD, we will usually resort to the efficient velocity-rescaling algorithm [56] implemented in the MD package GROMACS [57]. Here, the kinetic energy spread out over N f degrees of freedom is allowed to fluctuate according to a canonical distribution: The change in kinetic energy for each integration step is subjected to an equation of motion, incorporating both a relaxation term that reverts the kinetic energy to its ensemble average 1 2 N f k B T with a time constant τ , next to a Wiener process inherited from SD.…”

“…For a system composed of only two molecules A and B located at positions X and Y , respectively, the first-order contribution W (1) is given by the standard Poisson integral…”