Study of the Quantum Confinement Effects and Stability Properties of Small Nanoclusters of Bare and Hydrogenated Diamond
M. Yeganeha, F. Badieian Baghsiyahia, R. Pilevar Shahrib
aSchool of Natural Science, Kosar University of Bojnord, P.O. Box 94104455, Bojnord, Iran
bDepartment of Physics, Payame Noor University (PNU), P.O. Box 19395-3697, Tehran, Iran
Received: December 3, 2018; revised version April 10, 2019; in final form May 2, 2019
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Density functional theory, as implemented in SIESTA code, was utilized in this study to investigate the structural, electronic and stability properties of bare and hydrogenated small nanoclusters of diamond. The results obtained by studying different nanoparticles of diamond composed of 19, 50, and 104 carbon atoms, revealed that while the gap energy of hydrogenated nanodiamonds reduced from 8.2 to 6.5 eV by increasing the size of nanoparticles (number of carbon atoms), the bare nanodiamonds showed almost no gap energy except C19 sample which has the highest occupied molecular orbital-lowest unoccupied molecular orbital of about 0.33 eV. Electron affinity of hydrogenated samples was calculated and it was found that hydrogenated nanodiamond exhibits negative electron affinity. The quantum confinement effect found to be still significant for the sample larger than 1 nm i.e. the largest hydrogenated sample of C104H90 with a diameter of about 1.2 nm which showed greater gap energy in comparison to the bulk diamond. This achievement was explained considering electron affinity and partial density of states analysis. The calculated formation energy of the nanoparticles confirmed that the small hydrogenated nanoclusters of diamond have more stability compared to the bare nanodiamonds.

topics: nanodiamond, structural and electronic properties, electron affinity, quantum confinement effects, structural stability