Chemical bonding in initial building blocks of semiconductors: Geometrical structures and optical absorption spectra of isolated CdSe2+ and Cd2Se2+ species

Abstract

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From Cd‐Rich to Se‐Rich – The Manipulation of CdSe Nanocluster Structure and Optical Absorption

“…Nevertheless, the good qualitative agreement between experiment and theory provides strong evidence that the predicted GM structures of the non‐stoichiometric nanoclusters are actually formed in the molecular beam experiment. This also confirms that B3LYP/cc‐pVTZ‐PP as well as PBE0/cc‐pVTZ‐PP are well suited to describe the optical properties of Cd x Se y + clusters [26,28] . Absorption features of B3LYP calculations are more red‐shifted in comparison to PBE0 results.…”

“…With with the exception of Cd 4 Se 3 + , all atoms are two‐fold coordinated. For stoichiometric CdSe clusters it is known that the hexagonal planar Cd 3 Se 3 + structure serves as a building block of larger CdSe NPs [26–28] . This geometry motif can also be found in Cd 4 Se 3 + .…”

“…An in‐depth presentation of the general methodology and experimental details are described elsewhere, [26,28] therefore, only a brief overview is given here. CdSe clusters are generated by a pulsed laser vaporization source and detected with time‐of‐flight mass spectrometry.…”

“…Structural candidates of Cd x Se y + clusters with x=3, 4 and y=3, 4 are obtained by employing a genetic algorithm GA as described elsewhere [26,28,30] . All energetically lowest‐lying isomers are locally re‐optimised using NWChem v6.6 [31] at the PBE0/cc‐pVTZ‐PP [22,24–25] and B3LYP/cc‐pVTZ‐PP [23–25] level of theory with the respective effective core potential (ECP).…”

GIGA: a versatile genetic algorithm for free and supported clusters and nanoparticles in the presence of ligands

“…This functional and basis set choice has previously been found to give a good description of CdSe clusters. 47 The resulting structures are shown in Figure 5. Three [Cd 3 Se 3 (H 2 S) 3 ] + structures (Iso-I -Iso-III) were found which lie within an energy range of ∆E ≤ 0.10 eV.…”