The interaction of bright–dark two solitons. Top panel: density distributions of two solitons collisions in two components; (a1) for component q_2b and (b1) for component q_2d. Bottom panel: intensity profiles for both components at t = 0; panels (a2) and (b2) correspond to the component q_2b (thin blue curve) and the component q_2d (thick blue curve) respectively. It is seen that the two dark solitons collisions lead to a very high density hump above the background density in component q_2d. The parameters are w₁ = 1.8, v₁ = −1, w₂ = 1.8, v₂ = 1, φ₁ = 1.835π, and φ₂ = 0.