Ab initiostudy of the geometry and electronic structure of lead iodide semiconductor clusters

Layered anisotropic semiconductor clusters of the type ${\mathrm{Pb}}_{\mathrm{x}}$ ${\mathrm{I}}_{2\mathrm{x}}$ are studied in ab initio Hartree-Fock calculations that include relativistic effects. Total energies, internuclear distances, and net atomic charges are calculated. Large increases in the equilibrium iodine-lead interlayer distance result in as much as a 10% reduction of the in-plane internuclear separations and blueshifts in the electronic spectra, which are attributed to quantum size effects observed in recent experimental studies.