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Complex Low Energy Tetrahedral Polymorphs of Group IV Elements from First Principles.

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

He, Chaoyu 
Shi, Xizhi 
Clark, SJ 
Li, Jin 
Pickard, Chris J 

Abstract

The energy landscape of carbon is exceedingly complex, hosting diverse and important metastable phases, including diamond, fullerenes, nanotubes, and graphene. Searching for structures, especially those with large unit cells, in this landscape is challenging. Here we use a combined stochastic search strategy employing two algorithms (ab initio random structure search and random sampling strategy combined with space group and graph theory) to apply connectivity constraints to unit cells containing up to 100 carbon atoms. We uncover three low energy carbon polymorphs (Pbam-32, P6/mmm, and I4[over ¯]3d) with new topologies, containing 32, 36, and 94 atoms in their primitive cells, respectively. Their energies relative to diamond are 96, 131, and 112  meV/atom, respectively, which suggests potential metastability. These three carbon allotropes are mechanically and dynamically stable, insulating carbon crystals with superhard mechanical properties. The I4[over ¯]3d structure possesses a direct band gap of 7.25 eV, which is the widest gap in the carbon allotrope family. Silicon, germanium, and tin versions of Pbam-32, P6/mmm, and I4[over ¯]3d also show energetic, dynamical, and mechanical stability. The computed electronic properties show that they are potential materials for semiconductor and photovoltaic applications.

Description

Keywords

0912 Materials Engineering

Journal Title

Phys Rev Lett

Conference Name

Journal ISSN

0031-9007
1079-7114

Volume Title

121

Publisher

American Physical Society (APS)
Sponsorship
Royal Society (WM150023)
Engineering and Physical Sciences Research Council (EP/J010863/2)
Engineering and Physical Sciences Research Council (EP/P022596/1)
is supported by the National Natural Science Foundation of China (Grant No. 11704319), the National Basic Research Program of China (2015CB921103), the Natural Science Foundation of Hunan Province, China (Grant No. 2016JJ3118) and the Program for Changjiang Scholars and Innovative Research Team in University (IRT13093). CJP is supported by the Royal Society through a Royal Society Wolfson Research Merit award and the EPSRC through grants EP/P022596/1 and EP/J010863/2. Electro