Diffraction of trapped (CsI)(n)Cs+: the appearance of bulk structure

Area of Science:

• Physical Chemistry
• Materials Science
• Nanotechnology

Background:

• Understanding the structural evolution of ionic clusters is crucial for materials science.
• Cesium iodide (CsI) clusters exhibit complex structural behavior influenced by size and stoichiometry.
• Investigating cluster isomers provides insights into bulk material properties.

Purpose of the Study:

• To investigate the structural properties of cesium iodide (CsI) cluster cations, specifically (CsI)(n)Cs+ for n = 30-39.
• To determine the dominant structural motifs (rock salt vs. cesium chloride lattices) within this size range.
• To correlate cluster structures with bulk CsI lattice types and identify stable isomers.

Main Methods:

• Utilized trapped ion electron diffraction (TIED), a novel technique for studying cluster structures.
• Performed density functional calculations (DFT) to model potential energy surfaces and stable structures.
• Employed molecular dynamics (MD) simulations to explore structural transitions and stability.

Main Results:

• Observed diffraction patterns indicate contributions from both rock salt (NaCl) and cesium chloride (CsCl) lattice-derived structures at cluster size n = 32.
• The CsI cluster at n = 32 adopts a stable, closed-shell rhombic dodecahedron structure, consistent with the CsI bulk CsCl structure.
• For cluster sizes other than n = 32, the NaCl-derived structure is the dominant motif.

Conclusions:

• Cesium iodide cluster structures are size-dependent, with a distinct preference for the CsCl lattice at n = 32.
• The identified stable CsCl-derived isomer at n = 32 provides a link between small cluster behavior and bulk CsI properties.
• Trapped ion electron diffraction is a powerful technique for elucidating the structures of ionic clusters.