A combined DFT and molecular dynamics‐based study on structure and thermoelastic properties of carbonated‐fluorapatites

Abstract Carbonated fluorapatite (C‐FAP) is a promising ceramic for carbon capture, biomedical applications, and environmental remediation, yet uncertainties persist about the arrangement of carbonate ions and their influence on the different properties at high temperatures. This study combines density functional theory (DFT) and molecular dynamics (MD) simulations to study the stability, geometry, and thermoelastic properties of C‐FAPs with varying carbonate concentrations. The energetically favorable configurations of the three different types of substitutions are identified through DFT. However, only Type‐A is found to be thermodynamically stable from the convex hull analysis of 100 Na–Ca–C–F–O–P compositions; Type‐B and Type‐AB are unstable. MD simulations, benchmarked against DFT data, reveal: (i) loss of symmetry and anisotropic behavior, with Type‐A showing the maximum anisotropy; (ii) temperature‐driven elastic softening, with Type‐B exhibiting the smallest bulk modulus; and (iii) Arrhenius‐type carbonate diffusion, where Type‐B has the highest mobility and lowest activation energy. These results highlight that Type‐A offers better mechanical robustness, while Type‐B shows enhanced diffusion—making the former more suitable for long‐term storage and the latter better for utilization. Our study provides a predictive framework for tailoring C‐FAP properties and establishes a foundation for their use in high‐temperature carbon capture applications.