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oai:figshare.com:article/34024995 2026-09-29T16:05:19Z category_1 category_12 category_16 category_21 category_873 category_734 category_64 category_69 portal_63 item_type_6 month_year_09_2026

Beyond Optical Basicity: Role of O–Cl Bond Formation in CaCl₂‑Induced Silicate Network Disruption in Weathered Biotite Iwao Shimoyama (2495185) Yuji Baba (2534092) Biophysics Cell Biology Physiology Biotechnology Chemical Sciences not elsewhere classified Biological Sciences not elsewhere classified Cancer Inorganic Chemistry – si linkages weakening si – sup >–</ sup striking experimental observation predicting chemical reactivity fundamentally distinct mechanism optical basicity framework beyond optical basicity coordinated cl environments induce structural transformation thermal desorption spectroscopy tds shows cl combining cl k 3 </ sub 2 </ sub edge nexafs indicates mo calculations indicate cl k basicity additives tds ), phase transformation edge x edge near whereas high weathered biotite vacuum conditions uniquely induces silicate systems positively polarized nacl produces molecular orbital long served guiding principle findings suggest containing species The optical basicity framework has long served as a guiding principle for predicting chemical reactivity in silicate systems, yet it fails to explain a striking experimental observation: despite its extremely low optical basicity, CaCl₂ uniquely induces the phase transformation of weathered biotite (WB) at 600 °C–700 °C, whereas high-basicity additives such as CaO and CaCO₃ do not. Here, we address this paradox by combining Cl K-edge near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, thermal desorption spectroscopy (TDS), and molecular orbital (MO) calculations. Cl K-edge NEXAFS indicates the coexistence of Cl^– and positively polarized O-coordinated Cl environments, while TDS shows Cl-containing desorption products consistent with the formation of oxychlorine-containing species below the onset of phase transformation. In contrast, NaCl produces no detectable O–Cl bonding species and fails to induce structural transformation under vacuum conditions. MO calculations indicate that O–Cl bonds destabilize silicate frameworks by weakening Si–O–Si linkages more effectively than Si–Cl bonds. These findings suggest that O–Cl bond formation provides a fundamentally distinct mechanism for low-temperature silicate network disruption beyond conventional optical basicity theory. 2026-09-29T00:00:00Z Text Journal contribution 10.1021/acs.jpcc.6c03362.s001 https://figshare.com/articles/journal_contribution/Beyond_Optical_Basicity_Role_of_O_Cl_Bond_Formation_in_CaCl_sub_2_sub_Induced_Silicate_Network_Disruption_in_Weathered_Biotite/34024995 CC BY-NC 4.0