Average and local strain fields in nanocrystals
| Autor: | Seung-Yub Lee, Ismail C. Noyan, Shangmin Xiong |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Diffraction
Materials science Condensed matter physics Constitutive equation Linear elasticity Micromechanics 02 engineering and technology Crystal structure 010402 general chemistry 021001 nanoscience & nanotechnology Energy minimization 01 natural sciences General Biochemistry Genetics and Molecular Biology 0104 chemical sciences Lattice (order) 0210 nano-technology Powder diffraction |
| Zdroj: | Journal of Applied Crystallography. 52:262-273 |
| ISSN: | 1600-5767 |
| Popis: | This article presents a rigorous and self-consistent comparison of lattice distortion and deformation fields existing in energy-optimized pseudo-spherical gold nanoparticles obtained from real-space and powder diffraction strain analysis techniques. The changes in atomic positions resulting from energy optimization (relaxation) of ideally perfect gold nanoparticles were obtained using molecular dynamics modeling. The relaxed atomic coordinates were then used to compute the displacement, rotation and strain components in all unit cells within the energy-optimized (relaxed) particles. It was seen that all of these terms were distributed heterogeneously along the radial and tangential directions within the nanospheroids. The heterogeneity was largest in the first few atomic shells adjacent to the nanoparticle surface, where the continuity of crystal lattice vectors originating from the interior layers was broken because of local lattice rotations. These layers also exhibited maximum shear and normal strains. These (real-space) strain values were then compared with the average lattice strains obtained by refining the computed diffraction patterns of such particles. The results show that (i) relying solely on full-pattern refinement techniques for lattice strain analysis might lead to erroneous conclusions about the dimensionality and symmetry of deformation within relaxed nanoparticles; (ii) the lattice strains within such relaxed particles should be considered `eigenstrains' (`inherent strains') as defined by Mura [Micromechanics of Defects in Solids, (1991), 2nd ed., Springer]; and (iii) the stress/strain state within relaxed nanoparticles cannot be analyzed rigorously using the constitutive equations of linear elasticity. |
| Databáze: | OpenAIRE |
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