title: Reconstructing a solid-solid phase transformation pathway in CdSe nanosheets with associated soft ligands.
abstract: Integrated single-crystal-like small and wide-angle X-ray diffraction images of a CdSe nanosheet under pressure provide direct experimental evidence for the detailed pathway of transformation of the CdSe from a wurtzite to a rock-salt structure. Two consecutive planar atomic slips [(001) {110} in parallel and (102) {101}with a distortion angle of ∼40°] convert the wurtzite-based nanosheet into a saw-like rock-salt nanolayer. The transformation pressure is three times that in the bulk CdSe crystal. Theoretical calculations are in accord with the mechanism and the change in transformation pressure, and point to the critical role of the coordinated amines. Soft ligands not only increase the stability of the wurtzite structure, but also improve its elastic strength and fracture toughness. A ligand extension of 2.3 nm appears to be the critical dimension for a turning point in stress distribution, leading to the formation of wurtzite (001)/zinc-blende (111) stacking faults before rock-salt nucleation.
authors.affiliation: Cornell High Energy Synchrotron Source, Wilson Laboratory, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Zhongwu
authors.initials: Z
authors.lastname: Wang
authors.forename: Xiao-Dong
authors.initials: XD
authors.lastname: Wen
authors.forename: Roald
authors.initials: R
authors.lastname: Hoffmann
authors.forename: Jae Sung
authors.initials: JS
authors.lastname: Son
authors.forename: Ruipeng
authors.initials: R
authors.lastname: Li
authors.forename: Chia-Chen
authors.initials: CC
authors.lastname: Fang
authors.forename: Detlef-M
authors.initials: DM
authors.lastname: Smilgies
authors.forename: Taeghwan
authors.initials: T
authors.lastname: Hyeon
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D003198:Computer Simulation; D003460:Crystallization; D004548:Elasticity; D008024:Ligands; D008958:Models, Molecular; D008962:Models, Theoretical; D049329:Nanostructures / Q000737:chemistry*; D044367:Phase Transition; D011312:Pressure; D018036:Selenium Compounds / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D014961:X-Ray Diffraction; D015032:Zinc / Q000737:chemistry
chemical_list: D019187:Cadmium Compounds; D008024:Ligands; D018036:Selenium Compounds; C058667:cadmium selenide; D015032:Zinc