Curvature of the gravitational (Roche) potential near the inner and outer Lagrangian points around the donor star. The middle panel depicts an overall shape of the Roche potential in a binary in the corotating frame. The inner and outer Lagrangian points of the donor, indicated by a violet star and magenta cross, respectively, are where our computational domain is located. The $\stackrel{\sim }{x}$ axis of the domain is aligned with the binary axis and the z axis is parallel to the binary orbit axis. The left panels illustrate the significantly steeper curvature and shallower potential depth – both perpendicular (top) and parallel (bottom) to the binary axis – near the inner Lagrangian point than the outer Lagrangian point for a system where the donor and accretor have comparable masses (for instance, stellar binaries). The right panels show the same quantities for a case where the donor mass is significantly smaller than the accretor mass (for example, stellar extreme mass ratio inspiral). In this case, similar to the comparable mass ratio case, the potential near the outer Lagrangian point exhibits shallower curvature. However, the depths become comparable. In fact, the depths become equal as the ratio of the donor mass to the accretor mass approaches zero. The curvature of the potential near the Lagrangian points is primarily determined by the coefficients of the quadratic terms in the Taylor expansion of the Roche potential (Eq. (2)).