Elucidating Thermally Induced Structural and Chemical Transformations in Kaolinite using Reactive Molecular Dynamics Simulations and X-Ray Scattering Measurements

Lack of reliable predictive modeling methods and robust experimental techniques has hindered the rational design of hierarchical materials with desired structure-property-performance attributes suitable for extreme environments. With this context in mind, we explore the utility of ReaxFF reactive molecular dynamics (MD) simulations in combination with in-operando Wide Angle X-Ray Scattering (WAXS) and X-Ray Pair Distribution Function (PDF) analyses. To demonstrate the method, we consider kaolinite, a natural hierarchical material as the candidate and determine thermally induced chemical and structural transformations when heated from 298 to 1673 K. We first compare the key structural features from the PDF data and WAXS peaks obtained experimentally to those calculated from MD simulations. Upon observing excellent agreement, we proceed to elucidate the underlying chemical reaction mechanisms associated with dehydroxylation and sintering, identify intermediate and transition states and also estimate energy ...