Chemical trends in the optical properties of rocksalt nanoparticles

Abstract

The nature and magnitude of the optical gaps of rocksalt alkaline earth (MgO, CaO, SrO, MgS, MgSe) and transition metal chalcogenide (CdO, PbS) nanoparticles are studied using time-dependent density functional theory (TD-DFT) calculations on (MX)32 nanoparticles. We demonstrate, just as we previously showed for MgO, that TD-DFT calculations on rocksalt nanoparticles require the use of hybrid exchange-correlation (XC-)functionals with a high percentage of Hartree-Fock like exchange (e.g. BHLYP) or range-separated XC-functionals to circumvent problems related to the description of charge-transfer excitations. Concentrating on the results obtained with TD-BHLYP we show that the optical gap in rocksalt nanoparticles displays a wide range of behavior; ranging from large optical gaps stemming from a localized excitation involving corner atoms in alkaline earth oxides to a delocalized excitation and small optical gaps in the transition metal chalcogenides. Finally, we rationalize this wide range of behaviour in terms of differences in the degree to which the Coulombic interaction between the excited electron and hole is screened in the different nanoparticles, and relate it to the optical dielectric constants of the bulk materials the nanoparticles are made from.

Size and shape effects on the stability, electronic structure, and Raman spectroscopy of (SrO)n nanoclusters

“…Figure 1 gathers the structures obtained via the B3LYP/def2-SVP level of theory. As expected [19][20][21][22]25], the procedure used here to obtain the final structures does not change the shape of the clusters, only local modifications in the distances obtained between the Ca O [24] and the Sr O bonds were observed [21]. As a result, the majority of the systems are derivatives of cuboids, tubes, or polyhedrons 3D structures [24].…”

“…Additionally, due to the wide applicability of AEMO in heterogeneous catalysis [26][27][28], fuel cells [29,30], improving solar cells efficiency [31], and other general optical applications [7,19,32,33], systematic studies of finite size effects on the properties of those systems turn highly desirable to further progress in the area. Thus, AMEO clusters have drawn the attention of theoretical [19][20][21][22][23][24][25] and experimental [34][35][36][37][38][39][40][41][42] researchers.…”

Preparation of Cobalt Nanoparticles

“…From the viewpoint of creation of new technologies, transition metal NPs occupy a special place among other nanosized particles. They are of great interest due to their peculiar catalytic, [49–57] magnetic, [58–64] mechanical, [65–67] optical, [68–71] electronic, [72–74] and biological [75–79] properties. Most of these applications require chemically stable, well‐dispersed, and uniform‐sized particles, hence the rapid development of methods for the synthesis of metal NPs [80–85] .…”

Structural, spectral and optical properties of rocksalt Al,Mn-doped CdO: experimental and DFT studies

“…In the theoretical calculations, the optimized structure and geometry parameters of the Cd 32 O 32 cluster taken from the reference [11] were used, and the average bond distance between Cd and O atom was calculated at 2.348 Å in this geometry. All of clusters contain 64 atoms are shown in Figure 5a.…”

“…The x, y, z coordinates of the optimized structure of the rocksalt Cd 32 O 32 cluster were taken from reference [11]. These optimized structural parameters have been used in all calculations.…”