A scale-bridging Simulation Approach to an atomistic Understanding of Apatite-Protein Composites: Nucleation Mechanisms, Structure and Mechanical Properties

• Applicant: Professor Dr. Dirk Zahn
• Subject Area: Theoretical Chemistry: Electronic Structure, Dynamics, Simulation
• Term: from 2011 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 202938935

• Final Report Year: 2017

Final Report Abstract

The project involved scale-bridging simulation studies for the exploration of atomic-tomeso scale processes that account for the unique structure and mechanic properties of apatite-protein composites. As the atomic structure and composition of such complex biocomposites only partially is known, the first part (i) of our modelling studies was dedicated to realistic crystal nucleation scenarios of inorganic-organic composites. Starting from the association of single ions, insights ranged from the mechanisms of motif formation, ripening reactions and the self-organization of nanocrystals, including their interplay with growth-controlling molecular moieties. On this basis, (ii) reliable building rules for unprejudiced scale-up models were derived to model bulk materials. This was accomplished for (enamel-like) apatite-protein composites, encompassing up to million atom models to provide a realistic account of the 10 nm length scale, whilst model coarsening is used to reach µm length scales. On this basis, a series of deformation and fracture simulation studies were performed and helped to rationalize biocomposite hardness, plasticity, toughness, self-healing and fracture mechanisms. Complementing experimental work, these modelling studies provide particularly detailed insights into the relation of hierarchical composite structure and favorable mechanical properties.

Publications

• (2014) Shearing in a Biomimetic Apatite-Protein Composite: Molecular Dynamics of Slip Zone Formation, Plastic Flow and Backcreep Mechanisms. PLOS one 9: e93309
  Zahn D, Bitzek E
  (See online at https://doi.org/10.1371/journal.pone.0093309)
• (2016) Multi-Scale Modelling of Deformation and Fracture in a Biomimetic Apatite-Protein Composite: Molecular-Scale Processes Lead to Resilience at the µm-Scale, PLOS one 11: e0157241
  Zahn D, Duchstein P
  (See online at https://doi.org/10.1371/journal.pone.0157241)
• (2017) Multi-scale simulations of apatite-collagen composites: from molecules to materials” Front. Mater. Sci. 11: 1-12
  Zahn D
  (See online at https://doi.org/10.1007/s11706-017-0370-3)