A method for diffraction-based identification of annealing-produced restructuring of amorphous fullerene

TL;DR

This paper presents a diffraction-based method to analyze the structural properties of amorphous fullerene produced by vacuum annealing, using neutron or x-ray diffraction data and modeling with limited candidate carbon structures.

Contribution

The method introduces a novel approach combining diffraction pattern fitting with rigid body molecular dynamics to quantify amorphous fullerene structures.

Findings

Quantified average size and curvature of sp2 carbon structures.

Analyzed sensitivity of structural results to domain composition.

Applied method to samples annealed at various temperatures.

Abstract

A method is suggested for estimation of structural properties of amorphous fullerene and its derivatives produced by vacuum annealing. The method is based on the fitting of the neutron or x-ray powder diffraction patterns for scattering wave vector's modulus in the range from few units to several tens of inverse nanometers. The respective inverse problem assumes that the structured component of a sample can be described with a limited number, Nstr, of candidate sp2 carbon structures (fullerenes, flat and curved flakes with graphene-like atom arrangement) of a limited number of atoms, Natom. These structures are packed heterogeneously, in the domains with various average density of atoms and various degree of ordering of structures, using the Rigid Body Molecular Dynamics with variable parameter of pair interaction of atoms in the neighboring rigid-body nanostructures. The method is applied to interpreting the data of neutron diffraction by an amorphous fullerene annealed at temperatures 600, 800, 850, 900 and 1000 C. The results for Nstr equal to 36 and Natom in the range from 14 to 285 enabled us to quantify structural properties of the samples in terms of the average size and curvature of the sp2 carbon structures, and analyze sensitivity of results to the layout of these structures in the domains (mixture of various structures in each domain vs. mixture of domains of identical structures).