  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).

Materials Science;Computational Physics