Merger rate due to captures in BBH − BBH interactions as a function of the eccentricity (measured at $$f_{22}=10\mathrm{H}\mathrm{z}$$, as explained in Sect. 4.5). In blue, the results obtained from the TSUNAMI simulations. In green and yellow, the analytical model of Sections 4.1 and 4.5, obtained from the CMC data, and computed from the minimum and maximum a_IMS (Equation (28)), respectively. For clarity, the area between these lines is coloured in light grey.