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

TL;DR

This study employs theoretical methods to explore the geometries, electronic, and thermodynamic properties of quantum dot isomers, revealing significant energy variations and the sensitivity of dipole moments to isomer structures.

Contribution

It introduces a systematic global energy search technique to identify quantum dot isomers and predicts their properties, highlighting the importance of isomerism in QD behavior.

Findings

Heats of formation vary widely among isomers.

Dipole moments are highly sensitive to isomer geometry.

Stable isomers are more likely to be observed experimentally.

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.