Evaluation of nano- and mesoscale structural features in composite materials through hierarchical decomposition of the radial distribution function

Abstract

Composite materials possessing both crystalline and amorphous domains, when subjected to X‐ray and neutron scattering, generate diffraction patterns that are often difficult to interpret. One approach is to perform atomistic simulations of a proposed structure, from which the analogous diffraction pattern can be obtained for validation. The structure can be iteratively refined until simulation and experiment agree. The practical drawback to this approach is the significant computational resources required for the simulations. In this work, an alternative approach based on a hierarchical decomposition of the radial distribution function is used to generate a physics‐based model allowing rapid interpretation of scattering data. In order to demonstrate the breadth of this approach, it is applied to a series of carbon composites. The model is compared with atomistic simulation results in order to demonstrate that the contributions of the crystalline and amorphous domains, as well as their interfaces, are correctly captured. Because the model is more efficient, additional structural refinement is performed to increase the agreement of the simulation result with the experimental data. The model achieves a reduction in computational effort of six orders of magnitude relative to simulation. The model can be generally extended to other composite materials.

Local Structure Analysis and Modelling of Lignin‐Based Carbon Composites through the Hierarchical Decomposition of the Radial Distribution Function

“…In order to validate HDRDF 3 (henceforth referred to as HDRDF), as well as showcase the increased accuracy and functionality of this iteration of HDRDF, we apply it to neutron scattering (NS) RDF data of three hardwood derived carbon composites shown in Figure 1. The NS data used for HDRDF model validation was previously gathered and analyzed via MD by McNutt et al., experimentally characterized by Tenhaeff et al., and modeled with a previous version of HDRDF by García‐Negrón et al [13a,17,18] . A systematic analysis of crystalline domain shape, size, and volume fraction was conducted for the three samples, where crystallite size and crystalline volume fraction were varied for right parallelepiped, rod, sphere, and ellipsoid particle shapes and compared for best fit to the neutron scattering RDF data.…”

“…A detailed and rigorous explanation of the hierarchal decomposition theory is available in works by Oyedele et al. and García‐Negrón et al [17–18] . In this implementation of HDRDF, the following procedure is adopted.…”

“…Results from this analysis agreed well with the structural parameters found in the previous version of HDRDF published by García-Negrón et al, which showed the best model for this data uses spherical particles with increasing particle radius and decreasing crystalline volume fraction with the increasing carbonization temperature of the three carbon composites. [18] The RDFs for the three composites with their respective HDRDF models are shown in Figure 1 below with the optimized structural parameters shown in Table 1. We can see from Figure 1 that the magnitude of the peaks in the HDRDF model are consistent with the peak magnitudes from NS experiments.…”

“…Subsequent stages of decomposition occur to a point at which each component of the RDF can be represented with a tractable physics-based model. A detailed and rigorous explanation of the hierarchal decomposition theory is available in works by Oyedele et al and García-Negrón et al [17][18] In this implementation of HDRDF, the following procedure is adopted. For RDF components representing scattering by atoms within the same phase, the second level of decomposition is into atomistic and mesoscale components [Eq.…”

Study on Cellulose Acetate Butyrate/Plasticizer Systems by Molecular Dynamics Simulation and Experimental Characterization

“…In other words, it describes how the density varies with distance from a reference particle [ 29 ]. In a blend of various molecules, two different components tend to be compatible with each other if the RDF curve of mixed system is higher than each of their own [ 30 ]. Figure 3 shows the radial distribution functions (RDFs) of different CAB/plasticizer systems and those of their individual components.…”