Exploring the Correlation between Stability, Fluxionality, and Absorption Spectra of Ultrasmall CdSe Clusters: A Computational Study

Abstract

Various properties of (CdSe) 3n clusters (n = 1−9) were obtained using computational techniques. Using a simple force field, a simulated annealing technique was employed to explore the potential energy landscape and identify the isomers available at low temperatures. The lowest energy isomer was then optimized using density functional theory, and the quantities associated with their stability and optoelectronics were calculated. The possibility of fluxionality for a given range of temperatures and solvents was characterized by computing thermodynamic properties and inherent structure energies. All studied systems give rise to energetically stable hollow structures composed of six-and fourmembered rings that changed from spherical to tubular as the number of atoms increased. For a solvent of dielectric constant equal to three, fluxionality was observed at 300 K for almost all clusters considered. The corresponding band gap was found to be ∼3 eV and relatively independent of the size of the clusters in this size range. The absorption coefficients (as calculated from the dielectric functions) obtained from fluxionality effects are in agreement with the experimental absorption profiles.

First-Principles Study of the Electron–Hole Recombination Rate at the Interface of the CdSe Quantum Dot and TiO2 Substrate

“…The initial structures of the CdSe QDs are extracted from previous studies. − Five sizes are considered in our simulations, (CdSe) N of N = 6, 13, 19, 25, and 34 with diameters of 0.50, 0.85, 1.10, 1.20, and 1.40 nm, respectively. Considering the controversy on the most stable structures of (CdSe) 25 and (CdSe) 34 , ,, several more isomers for both QDs are collected and sent to structure relaxation.…”

Structural Evolution of Cadmium Selenide Clusters: An Unbiased Global Optimization Study of (CdSe)N for 5 ≤ N ≤ 80

“…As the macroscopic properties of materials are generally determined by their microscopic structures, it is crucial to have a comprehensive understanding of the low-energy structures of CdSe clusters of different sizes. This has garnered significant attention in both experiment and theory during the past several years. − …”

“…This involves performing GO in an energy landscape defined by interatomic potentials, followed by refining the obtained low-energy structures at a higher level of theory, such as DFT. In recent years, prescreening has been used to explore the low-energy structures of CdSe clusters. ,,,, For example, Farrow and co-workers employed an evolutionary algorithm to search both directly and after prescreening on the DFT energy landscape for (CdSe) N ( N = 1–12) and observed a transition from two-dimensional rings to three-dimensional structures as N increases . Nguyen and co-workers adopted a combination of structural enumeration, Monte Carlo search, and local optimization to study (CdSe) N ( N = 1–37) and identified spheroidal, tubular, cage-core, and wurtzite structures for different values of N . , Tan and co-workers employed the ab initio random structure searching (AIRSS) method to investigate the structures of (CdSe) N ( N = 2–34) and found the clusters gradually transformed from cage-like to bulk-like structures as N increased .…”

“…Nguyen and co-workers adopted a combination of structural enumeration, Monte Carlo search, and local optimization to study (CdSe) N ( N = 1–37) and identified spheroidal, tubular, cage-core, and wurtzite structures for different values of N . , Tan and co-workers employed the ab initio random structure searching (AIRSS) method to investigate the structures of (CdSe) N ( N = 2–34) and found the clusters gradually transformed from cage-like to bulk-like structures as N increased . López-Morales and co-workers used a simulated annealing technique with a simple force field to explore the energy landscape of (CdSe) 3 N ( N = 1–9) and obtained stable hollow structures composed of six- and four-membered rings, changing from spheres to tubes with an increase in N as determined by DFT calculations . However, the detailed structures of larger (CdSe) N with N > 37 remain unexplored due to their high degree of complexity.…”

“…34 Loṕez-Morales and co-workers used a simulated annealing technique with a simple force field to explore the energy landscape of (CdSe) 3N (N = 1−9) and obtained stable hollow structures composed of six-and fourmembered rings, changing from spheres to tubes with an increase in N as determined by DFT calculations. 36 However, the detailed structures of larger (CdSe) N with N > 37 remain unexplored due to their high degree of complexity.…”