38 research outputs found
Inversion of diffraction data for amorphous materials
The general and practical inversion of diffraction data-producing a computer
model correctly representing the material explored - is an important unsolved
problem for disordered materials. Such modeling should proceed by using our
full knowledge base, both from experiment and theory. In this paper, we
describe a robust method to jointly exploit the power of ab initio atomistic
simulation along with the information carried by diffraction data. The method
is applied to two very different systems: amorphous silicon and two
compositions of a solid electrolyte memory material silver-doped GeSe3 . The
technique is easy to implement, is faster and yields results much improved over
conventional simulation methods for the materials explored. By direct
calculation, we show that the method works for both poor and excellent glass
forming materials. It offers a means to add a priori information in first
principles modeling of materials, and represents a significant step toward the
computational design of non-crystalline materials using accurate interatomic
interactions and experimental information
Information-Driven Inverse Approach to Disordered Solids: Applications to Amorphous Silicon
© Physical Review Materials
Publisher\u27s Versio
Small-Angle X-Ray Scattering in Amorphous Silicon: A Computational Study
We present a computational study of small-angle x-ray scattering (SAXS) in amorphous silicon (α-Si) with particular emphasis on the morphology and microstructure of voids. The relationship between the scattering intensity in SAXS and the three-dimensional structure of nanoscale inhomogeneities or voids is addressed by generating large high-quality (α-Si networks with 0.1%–0.3% volume concentration of voids, as observed in experiments using SAXS and positron annihilation spectroscopy. A systematic study of the variation of the scattering intensity in the small-angle scattering region with the size, shape, number density, and the spatial distribution of the voids in the networks is presented. Our results suggest that the scattering intensity in the small-angle region is particularly sensitive to the size and the total volume fraction of the voids, but the effect of the geometry or shape of the voids is less pronounced in the intensity profiles. A comparison of the average size of the voids obtained from the simulated values of the intensity, using the Guinier approximation and Kratky plots, with that of the same from the spatial distribution of the atoms in the vicinity of void surfaces is presented
density-functional studies of 13-atom Cu and Ag clusters
The putative ground-state structures of 13-atom Cu and Ag clusters have been
studied using molecular-dynamics (AIMD) simulations based
on the density-functional theory (DFT). An ensemble of low-energy
configurations, collected along the AIMD trajectory and optimized to nearest
local minimum-energy configurations, were studied. An analysis of the results
indicates the existence of low-symmetric bilayer structures as strong
candidates for the putative ground-state structure of Cu and Ag
clusters. These bilayer structures are markedly different from a buckled
bi-planar (BBP) configuration and energetically favorable, by about 0.40.5
eV, than the latter proposed earlier by others. Our study reveals that the
structure of the resulting putative global-minimum configuration is essentially
independent of the nature of basis functions (i.e., plane waves versus
pseudoatomic orbitals) employed in the calculations, for a given
exchange-correlation functional. The structural configurations obtained from
plane-wave-based DFT calculations show a slightly tighter or dense first-shell
of Cu and Ag atoms than those from local-basis functions. A comparison of our
results with recent full-potential DFT simulations is presented.Comment: 5 pages, 5 figure