Crystal structure searching by free energy surface trekking: application to carbon at 1 TPa

18th APS-SCCM; 24th AIRAPT

Ishikawa, T.^1 ; Suzuki, N.^2 ; Shimizu, K.^1

KYOKUGEN, Center for Quantum Science and Technology under Extreme Conditions, Osaka University, 1-3 Machikaneyama, Osaka, Toyonaka

560-8531, Japan^1

Department of Pure and Applied Physics, Kansai University, 3-3-35 Yamate-cho, Osaka, Suita

564-8680, Japan^2

关键词: Ab initio crystal structures;    Free energy surface;    Local minimums;    Mechanically stable;    Metastable structures;    Pressure ranges;    Restoring forces;    Searching methods;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/500/16/162003/pdf
DOI  :  10.1088/1742-6596/500/16/162003

来源: IOP

【 摘 要 】

We have developed an ab-initio crystal structure searching method, free energy surface trekking (FEST). This method consists of an ascent-run and a descent-run. First, the system is forced to climb up a free energy surface following by the inversion of the restoring forces acting on the simulation cell (ascent-run). Then, the system climbs down the surface toward neighboring local minima according to the release from the constraint of the inversion immediately after the system crosses the ridges of the surface (descent-run). We have applied the FEST simulations to carbon at terapascal pressures and obtained a BC8-like structure with a tetragonal I41in addition to the earlier-predicted BC8, R8, and simple cubic structures. This structure is mechanically stable in the pressure range of at least 0.5-3.5 TPa, and has a potential to survive as a metastable structure in carbon at terapascal pressures.