TY - JOUR
T1 - Prediction of optically-active transitions in type-VIII guest-free silicon clathrate Si46
T2 - A comparative study of its physical properties with type-I counterpart through first-principles
AU - Mahammedi, Nassim Ahmed
AU - Ferhat, Marhoun
AU - Tsumuraya, Takao
AU - Chikyow, Toyohiro
N1 - Funding Information:
Author Nassim Ahmed Mahammedi would like to thank the Ministry of Higher Education and Scientific Research - Algeria, for providing scholarship to Japan in the frame of the “Programme National Exceptionnel PNE (Oct 2016 to Oct 2017)”. One of the authors, M.F., would like to acknowledge the partial financial support provided by the UWI at Mona under the new initiative grant F:16104P/ O:7505/A:760005/P:21.
Publisher Copyright:
© 2017 Author(s).
Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2017/11/28
Y1 - 2017/11/28
N2 - We have systematically studied the structural, electronic, and optical properties of two types of guest-free Si46 silicon clathrates using first-principles density-functional theory calculations. The properties are compared between two different crystal structures with the same chemical formula of Si46, type-I, and type-VIII. We apply a hybrid functional approach with the Becke, Lee-Yang-Parr (BLYP) functional and compare the electronic properties with those by generalized gradient approximation (GGA-PBE). The band structures of both clathrates calculated within the GGA indicate semiconducting (insulating) properties with indirect bandgaps of 1.38 and 1.36 eV for type-I and type-VIII, respectively. These band gaps increase to 1.60 and 1.62 eV by using the BLYP hybrid functional. The calculated optical absorption of type-I clathrate is slightly larger than that of type-VIII. Lastly, we also performed a symmetry analysis of optical transitions for both Si46 clathrates. It is found that optical transitions are dipole-allowed at the band-edge located along the Γ-Η line for Si46-VIII, while the transitions for type-I Si46 are forbidden by symmetry. It is hoped that this finding will motivate further investigations of optical capabilities of the silicon based type-VIII clathrates for photovoltaic and photonic devices.
AB - We have systematically studied the structural, electronic, and optical properties of two types of guest-free Si46 silicon clathrates using first-principles density-functional theory calculations. The properties are compared between two different crystal structures with the same chemical formula of Si46, type-I, and type-VIII. We apply a hybrid functional approach with the Becke, Lee-Yang-Parr (BLYP) functional and compare the electronic properties with those by generalized gradient approximation (GGA-PBE). The band structures of both clathrates calculated within the GGA indicate semiconducting (insulating) properties with indirect bandgaps of 1.38 and 1.36 eV for type-I and type-VIII, respectively. These band gaps increase to 1.60 and 1.62 eV by using the BLYP hybrid functional. The calculated optical absorption of type-I clathrate is slightly larger than that of type-VIII. Lastly, we also performed a symmetry analysis of optical transitions for both Si46 clathrates. It is found that optical transitions are dipole-allowed at the band-edge located along the Γ-Η line for Si46-VIII, while the transitions for type-I Si46 are forbidden by symmetry. It is hoped that this finding will motivate further investigations of optical capabilities of the silicon based type-VIII clathrates for photovoltaic and photonic devices.
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U2 - 10.1063/1.4999985
DO - 10.1063/1.4999985
M3 - Article
AN - SCOPUS:85036464484
VL - 122
JO - Journal of Applied Physics
JF - Journal of Applied Physics
SN - 0021-8979
IS - 20
M1 - 205103
ER -