Calculation of single chain cellulose elasticity using fully atomistic modeling

Cellulose nanocrystals, a potential base material for green nanocomposites, are ordered bundles of cellulose chains. The properties of these chains have been studied for many years using atomic-scale modeling. However, model predictions are difficult to interpret because of the significant dependence of predicted properties on model details. The goal of this study is to begin to understand these dependencies. We focus on the investigation on model cellulose chains with different lengths and having both periodic and nonperiodic boundary conditions, and predict elasticity in the axial (chain) direction with three commonly used calculation methods. We find that chain length, boundary conditions, and calculation method affect the magnitude of the predicted axial modulus and the uncertainty associated with that value. Further, the axial modulus is affected by the degree to which the molecule is strained. This result is interpreted in terms of the bonded and nonbonded contributions to potential energy, with a focus on the breaking of hydrogen bonds during deformation.