Simulation Data In Literature Research Articles

Bandgap atomistic calculations on hydrogen-passivated GeSi nanocrystals

We present a detailed study regarding the bandgap dependence on diameter and composition of spherical Ge-rich GexSi1−x nanocrystals (NCs). For this, we conducted a series of atomistic density functional theory (DFT) calculations on H-passivated NCs of Ge-rich GeSi random alloys, with Ge atomic concentration varied from 50 to 100% and diameters ranging from 1 to 4 nm. As a result of the dominant confinement effect in the DFT computations, a composition invariance of the line shape of the bandgap diameter dependence was found for the entire computation range, the curves being shifted for different Ge concentrations by ΔE(eV) = 0.651(1 − x). The shape of the dependence of NCs bandgap on the diameter is well described by a power function 4.58/d1.25 for 2–4 nm diameter range, while for smaller diameters, there is a tendency to limit the bandgap to a finite value. By H-passivation of the NC surface, the effect of surface states near the band edges is excluded aiming to accurately determine the NC bandgap. The number of H atoms necessary to fully passivate the spherical GexSi1−x NC surface reaches the total number atoms of the Ge + Si core for smallest NCs and still remains about 25% from total number of atoms for bigger NC diameters of 4 nm. The findings are in line with existing theoretical and experimental published data on pure Ge NCs and allow the evaluation of the GeSi NCs behavior required by desired optical sensor applications for which there is a lack of DFT simulation data in literature.

Molecular thermodynamics of binary polymer solutions using modified double lattice model: Chain length dependence of primary lattice

In a previous study we modified a double lattice model by introducing a new interaction parameter, which improved the mathematical approximation defect, and gave a new expression for the Helmholtz energy of mixing. In the model the universal constants Cβ and Cγ in the primary lattice were determined by comparing them with literature Monte Carlo simulation data, which is the only case for r1 = 1 and r2 = 100 (case I). In this study we introduce new universal constants, Cβ and Cγ, as a function of the chain length of a polymer in a solvent (case II) by comparing them with other literature simulation data for various polymer chain lengths. The proposed model is compared with polymer–solvent systems. In an upper critical solution temperature phase behavior the theoretical results of case II were improved over those of case I. However, in a lower critical solution temperature phase behavior those of case I were not very sensitive to Cβ and Cγ. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2627–2633, 1999

Force balance in a turbulent particulate channel flow

Turbulent flows of 70 μm copper particles and 50 μm glass particles in a channel are considered and investigated by large eddy simulations. Only the influence of the background turbulence on the motion of particles is considered and possible modifications of the structure of turbulence due to motion of particles are not accounted for. Mean velocity profiles and RMS levels are presented and are found to be in good agreement with earlier simulation data in literature. Differences between the statistical behavior of the two particle types are presented and discussed. The statistical correlations are used for a detail study of the interphase forces. The dominant contributions in the streamwise and in the wall-normal directions are pointed out.