First Principles Study of the Properties of a Tetragonal Germanium |
| Can Zhang, Dong-Dong Pang, Xue-Qian Huang, Han-Yu Xue, Zhen-Long Lv, Hong-Ling Cui
School of Physics and Engineering, Henan University of Science and Technology, No. 263 Kaiyuan Avenue, Luoyang 471023, China |
| Received: May 22, 2018; in final form September 14, 2018 |
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| Germanium is an important semiconductor having abundant phases of scientific interest. In this work, we studied the structural, electronic, vibrational, elastic and thermal conductivity properties of a tetragonal germanium via first-principles calculations. The results indicate that it is dynamically stable and there is a breathing vibrational mode at its Brillouin zone center. It is a weak metal according to the GGA-based calculation, but an indirect band-gap semiconductor with a gap of 0.24 eV based on the HSE06-functional calculation. According to the calculations performed by the HSE06 functional, both positive and negative hydrostatic pressures can first alter the band gap to be direct and then metallic. The crystal is mechanically stable but anisotropic. Its hardness is predicted to be 8.2 GPa, slightly lower than that of cubic diamond-type Ge. Based on the calculated phonon dispersion curves, its thermal conductivity as a function of temperature is predicted, giving a value of about 13.5 W m-1 K-1 at 300 K. |
DOI:10.12693/APhysPolA.134.1163 PACS numbers: 62.20.de, 63.20.D-, 66.25.+g, 71.20.-b |