Geometric and Electronic Structures as well as Thermodynamic Stability of Hexyl-Modified Silicon Nanosheet
首发时间:2014-05-30
Abstract:The successful synthesis and outstanding properties of graphene have promoted strong interest in studying hypothetical graphene-like silicon sheet (silicene). Very recently, two-dimensional silicon nanosheet (Si-NS) stabilized by hexyl groups was reported in experiment. We here present an atomic-level investigation of the geometric stability and electronic properties of Si-NS, by density functional calculations and molecular dynamics simulations. The most stable structure of the hexyl-modified Si-NS corresponds to the one in which the hexyl groups are regularly attached to both sides of the sheet, with the periodicity of the hexyl groups on the sheet being 7.17 ?, in good agreement with the experimental value of 7.1 ?. The electrostatic repulsion effect of the hexyl groups could be an important reason for the favorable structure. The electronic structure of the hexyl-modified Si-NS shows a direct band gap that is not sensitive to the length of the alkyl group but sensitive to the strain effect which can be used to tune the gap continuously within the whole strain range we considered. Finally, both the first-principles and the force-field based molecular dynamics simulations show that the most stable structure of the hexyl-modified Si-NS could maintain its geometric configuration up to 1000 K.
keywords: Materials science silicon nanosheet geometric calculations electronic calculations first-principles calucations
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烷基有机官能团修饰稳定单层二维硅纳米片
摘要:石墨烯材料的成功制备及其出色的物理化学性质引起了人们对类石墨烯材料(如硅烯)的研究兴趣。如今,烷基有机官能团修饰的硅二维纳米(Si-NS)已经在实验中成功被合成出来。本文采用密度泛函和分子动力学理论,从原子尺度下讨论了用烷基官能团修饰的方法对单层二维硅纳米片的稳定化作用及其材料的电子性质。几何结构分析表明,最稳定结构中烷基官能团均匀分布在二维硅纳米片上下表面,官能团周期间距为7.17 ?,与实验值7.1 ?相符。基团分布主要受到静电排斥作用的影响。电子结构分析发现,有机官能团修饰对二维硅纳米片电子结构的影响有限。其中,材料能隙对修饰的烷基链长度n不敏感,却对外部应力十分敏感。最后,基于第一性原理和基于力场的分子动力学计算结果都显示,用烷基官能团修饰的单层硅二维纳米片在1000 K温度下仍然具有良好的热力学稳定性。
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No.4595469974142139****
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