71st MSL Lecture (Dr. Ha-Jun Sung)
| Date/Time | 2018/08/06 11:00-12:00 |
|---|---|
| Place | 1F Meeting Room, Building R3 |
| Organizer | Laboratory for Materials and Structures |
| Contact | Professor Fumiyasu Oba (Ext. 5511) |
Subject & Detail
Speaker： Dr. Ha-Jun Sung
(Department of Physics, Korea Advanced Institute of Science and Technology (KAIST) )
Title：
Computational materials search for novel metallic C and Si allotropes using an inverse design method
Abstract:
With the recent advance of computational power, discovery and design of new materials are being revolutionized by computational materials science. Recently, we have developed a protocol for a crystal structure search, in which the conformational space annealing algorithm for global optimization is combined with first-principles density functional calculations, called AMADEUS [1]. The AMADEUS has been successfully used to predict new materials, such as silicon and carbon allotropes with optimal direct band gaps for photovoltaic applications, possible intermediate phase of boron on the transition pathway from α-B to γ-B, a new phosphorus allotrope called green phosphorus with high carrier mobility, and a two-dimensional triangular Kagome lattice of boron that exhibits the exotic electronic properties.
In this presentation, we will show the successful application of AMADEUS to predict a novel metallic allotropes of carbon [2] and silicon [3]. The new carbon allotrope, termed m-C8, consists of five-membered rings with sp3 bonding interconnected by sp2-bonded graphitic carbon networks. Analyzing the electronic band structure, we identify that m-C8 belongs to the class of topological nodal line semimetals. The new Si allotrope, termed P6/m-Si6, contains open channels embedded in a simple hexagonal lattice. The new Si6 phase can be obtained by removing Na atoms from a chemical precursor NaSi6 in the P6/m space group that is discovered using AMADEUS at high pressure. We find that both the P6/m-Si6 and P6/m-Si6 clathrates are stable and superconducting with the critical temperature of about 12 and 13 K at zero pressure, respectively.
References
[1] I.-H. Lee, Y. J. Oh, S. Kim, J. Lee, and K. J. Chang, Comp. Phys. Commun. 203, 110 (2016).
[2] H.-J. Sung, S. Kim, I.-H. Lee, and K. J. Chang, NPG Asia Mater. 9, e361 (2017).
[3] H.-J. Sung, W. H. Han, I.-H. Lee, and K. J. Chang, Phys. Rev. Lett. 120, 157001 (2018).
