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

We report an investigation of (CsI)(n)Cs+ cluster structures (n = 30-39) studied using the recently developed technique of trapped ion electron diffraction. Contributions to diffraction from both rock salt (NaCl) and cesium chloride lattice (CsCl) derived isomeric structures are observed at size n = 32. This size can form a closed shell rhombic dodecahedron corresponding to the CsI bulk structure. All other sizes, n not equal 32, are dominated by the NaCl structure. Density functional calculations and molecular dynamic simulations identify the presence of a stable CsCl lattice derived structure isomer which is consistent with these results.