The AXEAP2 program for Kβ X-ray emission spectra analysis using artificial intelligence.

The processing and analysis of synchrotron data can be a complex task, requiring specialized expertise and knowledge. Our previous work addressed the challenge of X-ray emission spectrum (XES) data processing by developing a standalone application using unsupervised machine learning. However, the task of analyzing the processed spectra remains another challenge.

AXEAP: a software package for X-ray emission data analysis using unsupervised machine learning.

The Argonne X-ray Emission Analysis Package (AXEAP) has been developed to calibrate and process X-ray emission spectroscopy (XES) data collected with a two-dimensional (2D) position-sensitive detector. AXEAP is designed to convert a 2D XES image into an XES spectrum in real time using both calculations and unsupervised machine learning. AXEAP is capable of making this transformation at a rate similar to data collection, allowing real-time comparisons during data collection, reducing the amount of data stored from gigabyte-sized image files to kilobyte-sized text files.

Dispersion and stability mechanism of Pt nanoparticles on transition-metal oxides.

The heterogeneous catalysts of Pt/transition-metal oxides are typically synthesized through calcination at 500 °C, and Pt nanoparticles are uniformly and highly dispersed when hydrogen peroxide (HO) is applied before calcination. The influence of HO on the dispersion and the stability of Pt nanoparticles on titania-incorporated fumed silica (Pt/Ti-FS) supports was examined using X-ray absorption fine structure (XAFS) measurements at the Pt L and Ti K edges as well as density functional theory (DFT) calculations. The local structural and chemical properties around Pt and Ti atoms of Pt/Ti-FS with and without HO treatment were monitored using in-situ XAFS during heating from room temperature to 500 °C.

Decoupling the metal insulator transition and crystal field effects of VO.

VO is a highly correlated electron system which has a metal-to-insulator transition (MIT) with a dramatic change of conductivity accompanied by a first-order structural phase transition (SPT) near room temperature. The origin of the MIT is still controversial and there is ongoing debate over whether an SPT induces the MIT and whether the T can be engineered using artificial parameters. We examined the electrical and local structural properties of Cr- and Co-ion implanted VO (Cr-VO and Co-VO) films using temperature-dependent resistance and X-ray absorption fine structure (XAFS) measurements at the V K edge.

Crystallization of Transition-Metal Oxides in Aqueous Solution beyond Ostwald Ripening.

The crystallization mechanism of transition-metal oxides (TMOs) in a solution was examined based on ZnO crystallization using in-situ x-ray absorption fine structure (XAFS) measurements at the Zn K edge and semi-empirical quantum chemistry (SEQC) simulations. The XAFS results quantitatively determine the local structural and chemical properties around a zinc atom at successive stages from Zn(NO) to ZnO in an aqueous solution. The results also show that a zinc atom in Zn(NO) ions dissolves in a solution and bonds with approximately three oxygen atoms at room temperature (RT).

The influence of structural disorder and phonon on metal-to-insulator transition of VO .

We used temperature-dependent x-ray absorption fine structure (XAFS) measurements to examine the local structural properties around vanadium atoms at the V K edge from VO films. A direct comparison of the simultaneously-measured resistance and XAFS regarding the VO films showed that the thermally-driven structural transition occurred prior to the resistance transition during a heating, while  this change simultaneously occured during a cooling. Extended-XAFS (EXAFS) analysis revealed significant increases of the Debye-Waller factors of the V-O and V-V pairs in the {111} direction of the R-phase VO that are due to the phonons of the V-V arrays along the same direction in a metallic phase.

Local Structural Properties and Growth Mechanism of ZnO Nanorods on Hetero-Interfaces.

We investigated the growth mechanism of ZnO(001) nanorods on SrTiO3(001) substrates. In the beginning of ZnO growth, a ZnO(110) film was developed on SrTiO3 substrates and then (001)-oriented ZnO nanorods grew on the ZnO(110) film. The strain energy of ZnO(110) growth on SrTiO3(001) planes was approximately 2.