Dresden 2011 – scientific programme
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BP: Fachverband Biologische Physik
BP 29: Posters: Biopolymers \& Biomaterials
BP 29.8: Poster
Thursday, March 17, 2011, 17:15–20:00, P3
Enhancing mechanical properties of calcite by Mg substitutions: A quantum-mechanical study — •Pavlina Elstnerova1, Martin Friak1, Tilmann Hickel1, Helge Otto Fabritius1, Dierk Raabe1, Andreas Ziegler2, Sabine Hild3, and Joerg Neugebauer1 — 1Max-Planck-Institut for Iron Research, Duesseldorf, Germany — 2University of Ulm, Ulm, Germany — 3Johannes Kepler University Linz, Linz, Germany
Nearly 90 percent of all animal species in nature protect themselves by a cuticle that represents a hierarchical biocomposite often containing calcite as a mineral stiffening component. Calcite crystals rarely occur in their stoichiometric state and contain impurities. Common impurities in these systems are Mg or P, their role however is still the topic of intense debates. We present results of a parameterfree quantummechanical study of thermodynamic, structural, and elastic properties of calcite single crystals containing Mg atoms. Density functional theory calculations were performed employing 30atomic supercells within the generalized gradient approximation (GGA). Based on the calculated thermodynamical results, the site preference of Mg atoms was determined. Examining the structural characteristics, the behavior of the carbonate group is shown to be nearly independent on either the volume or concentration of Mg atoms. Based on the computed elastic values, the Mg atoms are predicted to stiffen the calcite crystals, specifically to increase the bulk modulus, but also to increase local strains due to the large sizemismatch when substituting Ca atoms by Mg ones (Elstnerova et al., Acta Biomaterialia 6 (2010) 4506-4512).