Molecular Dynamics Study of Chemomechanical Response Mechanisms in Basalt for Carbon Sequestration

Understanding how reactive fluids alter rock-forming minerals at the molecular scale is critical for evaluating the durability of geological CO₂ storage. To address this, we used molecular dynamics (MD) simulations to quantify the structural and mechanical responses of quartz, clinochlore, diopside, and albite under H₂O-ScCO₂ conditions. All four minerals exhibit reductions in elastic modulus: albite 43.9%, diopside 27.6%, clinochlore 22.5%, and quartz 17.6%. These changes were accompanied by unit-cell expansion and structural relaxation. The energy partition shifts from bond-dominated to nonbonded interactions, most pronounced in albite and clinochlore. Radial distribution analyses show that the Si-O coordination remains close to four, preserving the tetrahedral framework, whereas the Al-O coordination in albite and clinochlore increases toward six, indicating a surface structural reorganization driven by the presence of H₂O-ScCO₂ and predefined cation vacancies, which effectively induces structural relaxation of the aluminosilicate framework, introduces structural disorder, and creates pathways for enhanced fluid permeation. In conclusion, these results reveal an atomistic weakening pathway in which hydroxylation and cation release enhance lattice disorder and reduce stiffness. The findings provide a mechanistic link between microstructural degradation and macroscopic weakening and inform long-term stability assessments of basaltic reservoirs for CO₂ storage.