Atomic structure of the continuous random network of amorphous C[(C6H4)2]2, PAF-1

TL;DR

This study reveals the atomic structure of amorphous PAF-1 as a continuous random network with tetrahedral carbon sites linked by biphenyl groups, confirmed by neutron scattering and molecular dynamics simulations.

Contribution

First detailed atomistic model of amorphous PAF-1 using neutron scattering and MD simulations, highlighting structural similarities to amorphous silica.

Findings

Neutron scattering matches MD model predictions.

Presence of a first sharp diffraction peak at Q=0.45 Å^{-1}.

Structural analogy between PAF-1 and amorphous silica.

Abstract

We demonstrate that the amorphous material PAF-1, C[(C6H4)2]2, forms a continuous random network in which tetrahedral carbon sites are connected by 4,4'-biphenyl linkers. Experimental neutron total scattering measurements on deuterated, hydrogenous, and null-scattering samples agree with molecular dynamics simulations based on this model. From the MD model, we are able for the first time to interrogate the atomistic structure. The small-angle scattering is consistent with Porod scattering from particle surfaces, of the form Q^{-4}, where Q is the scattering vector. We measure a distinct peak in the scattering at Q = 0.45 {\AA}^{-1}, corresponding to the first sharp diffraction peak in amorphous silica, which indicates the structural analogy between these two amorphous tetrahedral networks.