QUANTUM CHEMICAL STUDY ON THERMAL DECOMPOSITION MECHANISM OF CALCIUM CARBONATE.

A detailed quantum chemical calculation is performed at the MP2(full)/6-311G* level to explore the mechanism of calcium carbonate thermal decomposition. Four microscopic pathways are identified. The rate constants of rate-determining steps in four pathways are calculated over a temperature range 298–1200 K. The calculating results show that only path A (R(CaCO3) → IM1 → P(CaO + CO2)) and path B (R(CaCO3) → IMB1 → IMB2 → P(CaO + CO2) have contributions to the CaCO3 thermal decomposition, and path A may be more favorable than path B. The present theoretical studies may provide useful information in understanding reaction mechanism of metal carbonates at the molecular level. [ABSTRACT FROM AUTHOR]