A Muon Spectroscopic and Computational Study of the Microscopic Electronic Structure in Thermoelectric Hybrid Silicon Nanostructures

Abstract

Phenylacetylene capped silicon nanoparticles (Phenyl-SiNPs) have attracted interest as a novel thermoelectric material. Here we report a combined muon spectroscopic (µSR) and computational study of this material in solution to investigate microscopic electronic structure in this system. For comparison, the model molecular compound tetrakis (2-phenylethynyl) silane has also been investigated. µSR measurements have shown that the muon isotropic hyperfine coupling constant, Aµ, which depends on spin density at the muon, is greatly reduced for the Phenyl-SiNPs system when compared to the model compound. Results have also demonstrated that the temperature dependence of Aµ for the Phenyl-SiNPs is of opposite sign and proportionally larger when compared to the model compound. Ab initio DFT methods have allowed us to determine the muon addition site in the model compound, while a wider computational study using both DFTB+ and CASTEP offers a qualitative explanation for the reduced coupling seen in the Phenyl-SiNPs system and also the contrasting temperature dependence of Aµ for the two materials. Calculations suggest an increase in the density of electronic states at the energy level of the highest occupied molecular state for the Phenyl-SiNPs, even in the presence of an organic cap, suggesting a mechanism for enhanced electron transport in this system when compared to the tetrakis model compound.

MuSpinSim: spin dynamics calculations for muon science

“…This input files are also described in the supplementary information ([12]). Figures (6) show these two crystalline structures, where the distinctive feature between them is the different "bridge" that connects the two Fe atoms of the Fe-Mu-Fe muonide. This "bridge" comprises two S atoms, 3 C atoms and 6 H atoms, and in each structure the arch formed by the C atoms has a different bending, which affects the simulated ALC results.…”

“…MuSpinSim is the latest software tool to be added to the Muon Spectroscopy Computational Project (MSCP) 1 , a project aimed at developing software and methods to help µSR scientist to better interpret their results with the help of state-of-the-art computational techniques [3][4][5][6].…”

Magnetic structure and crystal field states ofPr2Pd3Ge5:μSRand neutron scattering investigations

“…The PBE exchange-correlation functional [40] was used in combination with autogenerated ultrasoft pseudopotentials. The software package PYMUON-SUITE has already shown good results for the modeling and interpretation of μSR experiments [41,42] and, in this particular case, four potential crystallographically inequivalent stopping sites were identified, which are shown in Fig. 8 marked as A, B, C, and D We estimated the internal fields at these muon stopping sites using the dipolar contribution calculated using the DIPOLECALC program [43].…”