Top views of 1D NWs. (a)–(e) Schematic models of CsPbI₃ NWs: (a) triangular prism containing two Cubic(001) surfaces for right-angle sides and one Cubic(110) surface for the hypotenuse (0°-triangular prism); (b) triangular prism having two Cubic(110) surfaces and one Cubic(001) surface (90°-triangular prism); (c) quadrangular prism with four Cubic(001) side surfaces (0°-quadrangular prism); (d) quadrangular prism with four Cubic(110) side surfaces (0°-quadrangular prism); (e) rectangular prism with Orth(010) and Orth(001)-CsI as the side surfaces. The ratio of longer and shorter edges of the rectangular cross-section is 1.22 using a criterion of maximizing the cross-section area under a given circumference. (f), (g) Schematic models of CsPbBr₃ NWs: (f) quadrangular prism with Orth(001)-PbBr as all the side surfaces; (g) quadrangular prism with (110) and (001) as the side surfaces.