Figure 3

F _i of idealized MNP with a bump. Left: models of idealized MNP with a bump located along the x-direction for θ = 0.4 rad (A), θ = 0.55 rad (B) and θ = 0.7 rad (C). Green dot in (A) represents the dipole. (D) is the modal of an idealized MNP with ring bump. Right: (a) F _x of MNP with a 0.5 nm-high-bump along the x-direction (dashed line) and y-direction (solid line) using an x-oriented dipole for θ = 0.4 rad (red line), θ = 0.55 rad (blue line) and θ = 0.7 rad (green line). (b) is the same as (a) except that the bump has 1.0-nm height. (c) F _x of MNP with a ring bump with 0.5-nm height using an x-oriented dipole for θ = 0.4 rad (red line), θ = 0.55 rad (blue line) and θ = 0.7 rad (green line). (d–f) shows results for a z-oriented dipole with the other parameters being the same as those in (a–c). F _i of idealized MNPs without a bump is shown for comparison (black dashed line).