Browsing by Author "Batyrow, Merdan"
Now showing 1 - 2 of 2
- Results Per Page
- Sort Options
ArticlePublication Open Access Accuracy limits of pair distribution function analysis in structural characterization of nanocrystalline powders by X-ray diffraction(Turkish Chemical Society, 2022) Baloochiyan, Abolfazl; Batyrow, Merdan; Öztürk, Hande; Mechanical Engineering; KAYMAKSÜT, Hande Öztürk; Baloochiyan, Abolfazl; Batyrow, MerdanWe report the minimum errors of structural parameters, namely lattice parameter, crystallite size, and atomic displacement parameters, expected from Pair Distribution Function (PDF) analysis of nanocrystalline gold powders for the first time by a self-consistent computational methodology. Although PDF analysis has been increasingly used to characterize nanocrystalline powders by X-rays, the current literature includes no established error bounds to be expected from the resulting structural parameters. For accurate interpretation of X-ray diffraction data, these error bounds must be determined, and the obtained structural parameters must be cleared from them. Our novel methodology includes: 1) simulation of ideal powder diffraction experiments with the use of the Debye scattering equation, 2) pair distribution function analysis of the diffraction data with the Diffpy-CMI analysis software, and 3) determination of the errors from PDF analysis of the simulated diffraction data by comparing them with real-space analysis of spherical gold nanocrystals that are 30 nm size and smaller. Our results show that except for the lattice parameters and even with an ideal crystalline powder sample and ideal diffraction data, the extracted structural parameters from PDF analysis diverge from their true values for the studied nanopowder. These deviations are dependent on the average size of the nanocrystals and the energy of the X-rays selected for the diffraction experiments, where lower X-ray energies and small-sized nanocrystalline powders lead to greater errors.Conference paperPublication Metadata only Size dependent change of mean square displacement in gold nanocrystals: A molecular dynamics simulation(Wiley, 2023-11-01) Batyrow, Merdan; Fındıkçı, İlknur Eruçar; Öztürk, Hande; Mechanical Engineering; FINDIKÇI, Ilknur Eruçar; KAYMAKSÜT, Hande Öztürk; Batyrow, MerdanThermally activated atomic vibrations significantly decrease the x-ray diffraction intensities of nanocrystalline powders. Hence their quantification is critical for accurate structural characterization of small nanocrystals by x-ray diffraction. In this study, atomic vibrations in the form of mean square displacements (MSDs) in 5, 10, 15, 20, and 30 nm diameter spherical gold nanocrystals were computed by molecular dynamics (MD) simulations at room temperature and below. A strong size and temperature dependency of MSD was observed from spherical gold nanocrystals. Moreover, these displacements increased radially from the center of the nanocrystals and reached a maximum at the surface layers due to the presence of undercoordinated surface atoms and their relatively unrestricted motions. High temperature simulations were performed to investigate the evolution of structural stability of nanoparticles with increasing temperature. Surface melting was observed before complete melting of nanocrystals. Results of this work will be useful to understand the effect of nanocrystal size on the amplitude of thermally activated atomic vibrations and their quantification in measured intensities by x-ray diffraction experiments.