Aberration corrected imaging of a carbon nanotube encapsulated lindqvist ion and correlation with density functional theory

80 kV aberration-corrected transmission electron microscopy (AC-TEM) of discrete [W₆O₁₉]^2- polyoxometalate ions mounted within double walled carbon nanotubes (DWNTs) allow high precision structural studies to be performed. W atom column separations within the octahedral W ₆ tungsten template can be visualized with sufficient clarity that correlation with full-scale density functional theory (DFT) can be achieved. Calculations performed on the gas phase and DWNT-mounted [W₆O ₁₉]^2- anions show good agreement, in the latter case, with measured separations between pairs of W₂ atom columns imaged within equatorial WO₆ octahedra and single W atoms within axial WO ₆ octahedra. Structural data from the tilted chiral encapsulating DWNT was also determined simultaneously with the anion structural measurements, allowing the nanotube conformation to be addressed in the DFT calculations.