**2. Simulation Details**

#### *2.1. Computational Domain and Structures*

Figure 1 shows the schematic of the molecular dynamics setup used in this study for CNT and BNNT. In this study, we used CNTs and BNNTs with chirality (6,6) and length 100 Å in all simulations. As the Z-distortion name suggests, the nanotube deformation is along the Z-direction; hence, a nanotube of length 100 Å gets distorted to 90, 110, and 120 Å for distortion values of 0.9, 1.1, and 1.2, respectively. To compare the effect of different deformations on water transport, at least one physical property has to be kept constrained. In this study, the length was kept constrained; hence, the Z-distortion nanotubes were modeled considerably long, and then they were truncated to have the length ~100 Å.

**Figure 1.** Schematic of molecular dynamics simulation setup: (**a**) boron nitride nanotube (BNNT) and (**b**) carbon nanotube (CNT).

The geometry of the perfect nanotube is shown in Figure 2a. The Z-distortion is induced in the perfect nanotube either by stretching or compressing along Z-axis, which increases or decreases the length of the nanotube, respectively. The stretch factor is given by Z'/Z0, where Z' is the total length after the perfect nanotube is distorted in the Z-direction [6]. The Z-distorted nanotube is shown in Figure 2b. The nanotube with the twist is shown in Figure 2c. The screw factors for the twisted nanotubes are given as β/Z0, where β is the twist angle and Z0 is the length of the perfect nanotube. When an equal amount of force is applied in the positive and negative X or Y direction, XY-distorted carbon nanotubes can be obtained, as shown in Figure 2d. The XY-distorted nanotubes have an elliptical cross-section with ellipse factor ΔX/ΔY.

**Figure 2.** Perfect nanotube and different types of deformed nanotubes: (**a**) perfect nanotube; (**b**) Z-distortion nanotube (stretch factor: Z'/Z0); (**c**) twisted nanotube (screw factor: β/Z0); and (**d**) XY-distortion nanotube (ellipse factor: e = ΔX/ΔY).

The perfect (6,6) CNT has a radius of 4.068 Å and bond length of 1.421 Å, whereas a perfect (6,6) BNNT has a radius of 4.211 Å and bond length of 1.47 Å. The description of the dimensions of the nanotubes is given in Table 1.


**Table 1.** Dimensions of different nanotubes used in this study. Z-distortion nanotube (stretch factor: Z'/Z0), twisted nanotube (screw factor: β/Z0), and XY-distortion nanotube (ellipse factor: e = ΔX/ΔY).
