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Research
_Projects
Rose-X
High-Throughput simulation of powder scattering data.
A novel algorithm is developed for high-performance computing of accurate powder scattering/diffraction patterns via solution of the Debye scattering equation. A full-precision pair distribution function is computed by exploiting the series expansion of the error between calculated and equispace-sampled pair distances of atoms. Based on the propagation of uncertainty, the new algorithm provides results more accurate than brute-force calculation. Accurate intensities are calculated in the small-angle region, whereas anomalous (possibly negative) values are often returned using brute-force algorithms. The software application implementing this algorithm runs on a cluster of CPU/GPU multi-core processors and allows rapid simulation for atomistic models of materials composed of several million atoms. As an example, the profile for a 25 million atom microstructure was solved in a couple of hours. Moreover, the pair distribution function allows for evaluation of multiple powder diffraction profiles with different scattering range and resolution.
Ancora 1
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STAR-MiSt
Scattering Tool to Advance Research of Materials Structure.
We develop a modern graphic-interface framework to algorithms for analysis of powder scattering/diffraction data. The interface provides an easy control of complex analysis parameters. Oriented to user audience with little to none computational knowledge (e.g., laboratory experimentalists), the new application will serve future method developments. The framework is developed as an open-source library for efficient solution of material structure-microstructure, which is capable of exploiting a wide scenario of hardware architectures. It comprise different algorithms, such as a massively parallel library for solution of the Debye scattering equation. It provides a simple/systematic interface to third-party simulation tools. Integration of within third-party software packages such as: PM2K, Discus, and PM2K will is directly explored.
Ancora 2
WPDFM
Whole Pair Distribution Function Modelling.
Methods for analyzing either the traditional diffraction profile or the pair distribution function (PDF) differ in how the information is accessed and in the approximations usually applied. Any variation of structural and microstructural features over the whole sample affects the Bragg peaks as well as any diffuse scattering. Here, models based on Bragg's law are used to facilitate the computation of a whole PDF and then model powder-scattering data via the Debye scattering equation. The whole PDF is decomposed into the independent directional components, and the number of atom pairs separated by a given distance is statistically estimated using the common-volume functions. This approach overcomes the need for an atomistic model of the material sample and the computation of billions of pair distances. The results of this combined method are in agreement with the explicit solution of the DSE. Most importantly, the method exploits the strengths and different sensitivities of the Bragg and Debye theories.
Ancora 3
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Disorder in NanoMaterials
Engineered Disorder in Nanostructured Materials.
We aim to understand the relation between atom-pair interactions, the local deformation of the crystalline structure, and the resulting long-range lattice distortion in multi-component core@shell nanocrystals. This is essential to design a crystal microstructure that fully exploits the fundamental mechanisms underlying structure-dependent properties. Current studies are insufficient because they do not provide accurate enough information on a large collection of particles and they yield average information over different component regions. We exploit an enhanced analysis of experimental powder scattering data directly based on numerical simulations to bridge the detailed view of atomistic simulations with the information from a sample of thousands of millions of particles. Artificial Intelligence is used to predict the PDF’s change and for replacing cumbersome trial-and-error approach, widely employed by studies that combine experimental and simulation investigations.
Ancora 4
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