Isomerism in Quantum Dots: Geometries, Band Gaps, Dipole Moments, Ionization Energies and Heats of Formation

Abstract

Quantum dots (QDs) are applied in a variety of fields ranging from photovoltaics to biomedical imaging. Even the smallest QDs present a complicated potential energy surface characterized by a large set of stationary points. Each local minimum is an isomer of QD of given composition. An established theoretical methodology is hereby employed to obtain geometries of the QD isomers (Cd16Se16, Cd16Se16, Zn16S16, Zn16Se16) and predict their fundamental electronic and thermodynamic properties. Significantly scattered heats of formation, with an amplitude up to 1304 kcal mol-1 in Cd16S16, were found for the most and the least thermodynamically stable isomers of QDs. The most shallow transition points can unlikely be observed in the experiments at finite temperature, since they are able to transform into more stable isomers upon thermal motion. Dipole moment is the most sensitive property to the QD isomer geometry. A global energy search technique was demonstrated to be an efficient tool to systematically identify isomers of QDs.