Program

O.25 -- Oral, NCTP-42

Date: Wednesday, 2 August 2017

Time: 16h40 - 17h00

Molecular dynamics study of crystallization of supercooled liquid and amorphous silicene

Nguyen Truong Long (1), Huynh Anh Huy (1) , Vo Van Hoang (2), Truong Quoc Tuan (3), Pham Van Phuoc Em (3)

(1) Dept. of Physics Education, School of Education, Can Tho University, Can Tho City (2) Comp. Phys. Lab, HoChiMinh City Univ. of Technology, Vietnam National University – HoChiMinh City (3) Dept. of Physics, Faculty of Natural Sci., Can Tho Univ., Can Tho - Vietnam

Abstract Crystalline-Amorphous transition under isothermal condition of supercooled liquid and amorphous silicene (a-silicene) models has been studied via molecular dynamics (MD) simulation with Stillinger-Weber (SW) interaction potential. Supercooled liquid and a-silicene models containing 10000 atoms are obtained by rapid cooling process from the melts. At each given temperature below and above Tg, models are annealed for 10 nanoseconds in order to investigate aging effect on two-dimensional structural arrangement of disordered Si-atoms. Time dependence thermodynamic and structural quantities are analyzed including total energy, radial distribution function (RDF), coordination number, interatomic distance, ring and bond-angle distribution. Insights of “natural” re-formation process of disorder state models via 2D visualization of atomic configurations is presented. Our calculation shows that 2D-crystallization of supercooled liquid and a-silicene exhibits a first-order behavior, however, the aging effect takes place almost immediately after relaxation. Atomic mechanism of crystallization is studied in details during annealing process and we clarify novel scenario of crystallization. Homogenous natural quenched-in nucleated atoms have a tendency to aggregate into larger clusters in 2D Si supercooled liquid sheet. In contrast, the phase transition of a-silicene shows a partial crystallization and crystal clusters are found to be heterogeneously grown in models below Tg. Crystalline formation below Tg results in a quasi-equilibrium state with a large amount of defects after a long relaxation time. In all crystallized models, we found that the existence of low-numbered ring chains which may play an important role in controlling the crystal structure in practice. Acknowledgements This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under Grant 103.02-2016.88.

Presenter: Nguyen Truong Long