Lu–H–N Phase Diagram from First-Principles Calculations
Fankai Xie1,2†, Tenglong Lu1,2†, Ze Yu1,2, Yaxian Wang1, Zongguo Wang3, Sheng Meng1,2,4*, and Miao Liu1,4,5*
1Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China 2School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China 3Computer Network Information Center, Chinese Academy of Sciences, Beijing 100083, China 4Songshan Lake Materials Laboratory, Dongguan 523808, China 5Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
Abstract：Employing a comprehensive structure search and high-throughput first-principles calculation method on 1561 compounds, the present study reveals the phase diagram of Lu–H–N. In detail, the formation energy landscape of Lu–H–N is derived and utilized to assess the thermodynamic stability of each compound that is created via element substitution. The result indicates that there is no stable ternary structure in the Lu–H–N chemical system, however, metastable ternary structures, such as Lu$_{20}$H$_{2}$N$_{17}$ $(C2/m)$ and Lu$_{2}$H$_{2}$N ($P\bar{3}m1$), are observed to have small $E_{\rm hull}$ ($ < 100$ meV/atom). It is also found that the energy convex hull of the Lu–H–N system shifts its shape when applying hydrostatic pressure up to 10 GPa, and the external pressure stabilizes a couple of binary phases such as LuN$_{9}$ and Lu$_{10}$H$_{21}$. Additionally, interstitial voids in LuH$_{2}$ are observed, which may explain the formation of Lu$_{10}$H$_{21}$ and LuH$_{3-\delta}$N$_{\epsilon}$. To provide a basis for comparison, x-ray diffraction patterns and electronic structures of some compounds are also presented.
2023, Vol. 40 
