Si96: A New Silicon Allotrope with Interesting Physical Properties.

Qingyang Fan,Junqin Zhang,Peikun Zhou,Qun Wei,Changchun Chai,Yintang Yang

doi:10.3390/ma9040284

Qingyang Fan, Junqin Zhang + Show 4 more

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https://doi.org/10.3390/ma9040284

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Abstract

The structural mechanical properties and electronic properties of a new silicon allotrope Si96 are investigated at ambient pressure by using a first-principles calculation method with the ultrasoft pseudopotential scheme in the framework of generalized gradient approximation. The elastic constants and phonon calculations reveal that Si96 is mechanically and dynamically stable at ambient pressure. The conduction band minimum and valence band maximum of Si96 are at the R and G point, which indicates that Si96 is an indirect band gap semiconductor. The anisotropic calculations show that Si96 exhibits a smaller anisotropy than diamond Si in terms of Young’s modulus, the percentage of elastic anisotropy for bulk modulus and shear modulus, and the universal anisotropic index AU. Interestingly, most silicon allotropes exhibit brittle behavior, in contrast to the previously proposed ductile behavior. The void framework, low density, and nanotube structure make Si96 quite attractive for applications such as hydrogen storage and electronic devices that work at extreme conditions, and there are potential applications in Li-battery anode materials.

Highlights

Searching for novel silicon allotropes has been of great interest over the past several decades and has been extensively studied
It is well known that the regular arrangement of nanotubes can enhance the efficiency of the hydrogen storage of nanotubes [19]
The Si96 can be expected to have a good ability for hydrogen storage

Summary

Introduction

Searching for novel silicon allotropes has been of great interest over the past several decades and has been extensively studied. Many semiconductor silicon structures that have an indirect band gap have been proposed, such as the M phase, Z phase [2], Cmmm phase [3], body-centered-tetragonal. Many semiconductor silicon structures with a direct band gap have been reported, such as P21 3 phase [12], oF16-Si, tP16-Si, mC12-Si, and tI16-Si [13]. Silicon structures with metallic properties have been reported, such as the β-Sn phase, R8 phase [14], and Ibam phase [15]. All of the previous studies have opened the possibility of a broader search for new allotropes of silicon that possibly exhibit novel properties

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