Programme

P.26 -- Poster, VCTP-44

Date: Tuesday, 30 July 2019

Time: 08:30 - 10:00

Molecular dynamics simulation of microstructure and atom-level mechanism of crystallization pathway in iron nanoparticle

Giap Thi Thuy Trang (1), Pham Huu Kien (2), Pham Khac Hung (1) and Nguyen Thi Thanh Ha (1)

(1) Department of Computational Physics, Hanoi University of Technology, 1 Dai Co Viet, Hanoi Viet Nam (2) Department of Physics, Thainguyen University of Education, No. 28 Luong Ngoc Quyen, Thainguyen, Vietnam

Molecular dynamics simulation is used to study iron nanoparticles containing 5000 atoms at temperatures ranging from 300 K to 900 K. The crystallization and structure evolution was analyzed through pair radial distribution function, angle distribution, transition to different x-types, where x is the bcc, fcc-hcp, ico, 14, 12 and dynamical local structure parameters. The simulation showed that the structure of amorphous NP consists of two parts: the core has the structure similar to the one of bulk counterpart and the surface has more porous structure. The crystallization occurred when NP was annealed at 750 K, 800 K, 900 K for 40 ns. We found that amorphous NP is crystallized via transformations of amorphous type to bcc-type atoms. Moreover, the crystallization pathway comprises intermediate states between amorphous and crystalline ones. At the early stage a large cluster of Cryst-atom formed is located in a middle layer of NP. Then this cluster grows up and the parameter for it increases rapidly. At the final stage the cluster of Cryst-atom is located in a region covered a major part of NP. The growth of crystal cluster happens parallel with changing its microstructure. We also found that the structure of fully crystalline NP is strongly heterogeneous and consists of three separate regions with amorphous, crystal-like and bcc-crystal structure.

Presenter: Giap Thi Thuy Trang