2042 KSME International Journal, VoL 18 No. 11, pp. 2042~2048, 2004 Molecular Dynamics Study on External Field Induced Crystallization of Amorphous Argon Structure Seungho Park*, Sung San Cho Department of Mechanical and System Design Engineering, Hongik University, Seoul 121-791, Korea Joon Sik Lee School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151- 742, Korea Young Ki Choi School of Mechanical Engineering, Chung-Ang University, Seoul 156-756, Korea Ohmyoung Kwon School of Mechanical Engineering, Korea University, Seoul 136-701, Korea A molecular dynamics study has been conducted on an external-force-field-induced iso- thermal crystallization process of amorphous structures as a new low-temperature athermal crystallization process. An external cyclic-force field with a dc bias is imposed on molecules selected randomly in an amorphous-phase of argon. Multiple peaks smoothed out in the radial distribution functions for amorphous states appear very clearly during the crystallization process that cannot be achieved otherwise. When the amorphous material is locally exposed to an external force field, crystallization starts and propagates from the interfacial region and crystallization growth rates can be estimated. Key Words:Molecular Dynamics Simulation, Crystallization, Amorphous Structure Nomenclature A B F g L m N YO T x,y,z Greek P G Amplitude of external force DC bias for external fields External force Radial distribution function Simulation domain size Molecular mass Total number of molecules Inter-distance between molecules i and j Temperature Cartesian coordinates Symbols Energy parameter Number density Length parameter * Corresponding Author, E-mall : spark @ hongik.ac.kr TEL : +82-2-320-1632; FAX : +82-2-322-7003 Department of Mechanical and System Design Engi- neering, Hongik University, Seoul 121-791, Korea. (Manuscript Received January 3, 2004; Revised August 11, 2004) : Potential function r : Time Superscript * : Dimensionless 1. Introduction The objective of present study is to investigate the constant-temperature external force field in- duced crystallization of an amorphous material without crystalline seeds, using the molecular dy- namics (MD) simulation technique. Since the crystallization from amorphous structure can be achieved more quickly as the coordination num- bers of the constituent atoms increase (Tanaka et al., 1999), the crystallization of Lennard-Jones molecules are investigated as a first step towards the external force field-induced crystallization of an amorphous material, rather than silicon. The coordination numbers for Lennard-Jones and silicon atoms are 12 and 4, respectively.