sp(3)-hybridized framework structure of group-14 elements discovered by genetic algorithm

MC Nguyen and X Zhao and CZ Wang and KM Ho, PHYSICAL REVIEW B, 89, 184112 (2014).

DOI: 10.1103/PhysRevB.89.184112

Group-14 elements, including C, Si, Ge, and Sn, can form various stable and metastable structures. Finding new metastable structures of group-14 elements with desirable physical properties for new technological applications has attracted a lot of interest. Using a genetic algorithm, we discovered a new low-energy metastable distorted sp(3)-hybridized framework structure of the group-14 elements. It has P4(2)/mnm symmetry with 12 atoms per unit cell. The void volume of this structure is as large as 139.7 angstrom(3) for Si P4(2)/mnm, and it can be used for gas or metal-atom encapsulation. Band-structure calculations show that P4(2)/mnm structures of Si and Ge are semiconducting with energy band gaps close to the optimal values for optoelectronic or photovoltaic applications. With metal-atom encapsulation, the P4(2)/mnm structure would also be a candidate for rattling-mediated superconducting or used as thermoelectric materials.

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