Tangential Ligand-Induced Strain in Icosahedral Au13

A quantitative comparison of first principles calculations with extended x-ray absorption fine structure and transmission electron microscopy measurements provides strong evidence that Au$_{13}$ nanocrystals are stabilized in a slightly distorted icosahedral structure by on-top phosphine ligands and a combination of on-top and bridging thiol ligands. Importantly, the ligands change the icosahedral strain (i.e. the radial- tangential bond length ratio) significantly, with the tangential bonds within the Au core exhibiting much more disorder than the radial ones.