LAUSR

Nucleation at different temperature levels can provide quantitative insights into the energy barrier associated with sub‐molecular nuclei. The accurate calculation of nucleation rates, thermodynamics, and interfacial energy for extremely small nanoclusters (1−2 nm) remains a challenge at high temperatures. Here, Eα${E}_{\alpha}$ , ΔG,ΔH,ΔSandAα$\Delta G,\Delta H,\Delta S\ \mathrm{and}\ {A}_{\alpha}$ are computed to estimate the nucleation rate of ultra‐small CaCO3 pre‐nucleation clusters (0.85 nm) from thermogravimetric analysis (TGA) experimental values in the temperature range from 555 to 795 K, by adopting the most accurate iterative iso‐conversional method and random nucleation dependent differential function f(α)$f(\alpha )$ , respectively. On the basis of these analyses, four mathematical models are presented for computing nucleation rates (nucleiμm−2min−1)$(\mathrm{nuclei}\ \umu{\mathrm{m}}^{-2}\,{\min}^{-1})$ and interfacial energy (mJ m−2 variation with temperature and conversion for CaCO3 prenucleation clusters. Furthermore, experimental validation is also carried out in order to assess the existence of nucleation in CaCO3 pre‐nucleation clusters at high temperatures (500 °C) using X‐ray diffraction and experimental z(α) master plots. The TGA can be used to predict and understand nucleation rates for various nano systems.