First principle investigation of the mechanical properties of natural layered nanocomposite: Clinochlore as a model system for heterodesmic structures

For many technological applications, it is of paramount importance to study the mechanical behaviour of heterogeneous multi layered materials, and how they develop at the nanoscale. By employing a nature-based approach (learning from Nature) and ab initio Density Functional Theory (DFT) methods, in the present work we report a detailed mechanical investigation of a very interesting natural heterodesmic nanocomposite material made of alternated stacked magnesium hydroxide (brucite-like) and hydroxysilicate (talc-like) layers. This mineral phase has very interesting surface and bulk crystal-chemical properties, but its elastic behaviour is still not well known. Both the hydrostatic compression and the second order elastic constants were reported. An ideal, stoichiometric structure and a cation-substituted one were considered to stress the power of DFT methods in tailoring the properties, and the results were presented and consistently discussed with the experimental data available in literature. This study showed that the DFT/B3LYP-D* approach represents a powerful route to investigate other layered structures of multilayer composites for tailoring of specific mechanical properties.