RESUMO
Ionic liquids are a unique class of materials with several potential applications in electrochemical energy storage. When used in electrolytes, these highly coordinating solvents can influence device performance through their high viscosities and strong solvation behaviors. In this work, we explore the effects of pyrrolidinium cation structure and Li+ concentration on transport processes in ionic liquid electrolytes. We present correlated experimental measurements and molecular simulations of Li+ mobility and O2 diffusivity, and connect these results to dynamic molecular structural information and device performance. In the context of Li-O2/Li-air battery chemistries, we find that Li+ mobility is largely influenced by Li+-anion coordination, but that both Li+ and O2 diffusion may be affected by variations of the pyrrolidinium cation and Li+ concentration.
RESUMO
This paper reports an updated parameterization for a CdTe bond order potential. The original potential is a rigorously parameterized analytical bond order potential for ternary the Cd-Zn-Te systems. This potential effectively captures property trends of multiple Cd, Zn, Te, CdZn, CdTe, ZnTe, and Cd(1-x)Zn(x)Te phases including clusters, lattices, defects, and surfaces. It also enables crystalline growth simulations of stoichiometric compounds/alloys from non-stoichiometric vapors. However, the potential over predicts the zinc-blende CdTe lattice constant compared to experimental data. Here, we report a refined analytical Cd-Zn-Te bond order potential parameterization that predicts a better CdTe lattice constant. Characteristics of the second potential are given based on comparisons with both literature potentials and the quantum mechanical calculations.
RESUMO
Cd(1-x)Zn(x)Te (CZT) crystals are the leading semiconductors for radiation detection, but their application is limited by the high cost of detector-grade materials. High crystal costs primarily result from property nonuniformity that causes low manufacturing yield. Although tremendous efforts have been made in the past to reduce Te inclusions/precipitates in CZT, this has not resulted in an anticipated improvement in material property uniformity. Moreover, it is recognized that in addition to Te particles, dislocation cells can also cause electric field perturbations and the associated property nonuniformities. Further improvement of the material, therefore, requires that dislocations in CZT crystals be understood and controlled. Here, we use a recently developed CZT bond order potential to perform representative molecular dynamics simulations to study configurations, energies, and mobilities of 29 different types of possible dislocations in CdTe (i.e., x = 1) crystals. An efficient method to derive activation free energies and activation volumes of thermally activated dislocation motion will be explored. Our focus gives insight into understanding important dislocations in the material and gives guidance toward experimental efforts for improving dislocation network structures in CZT crystals.
