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분자동력학과 몬테카를로의 혼성 분자시뮬레이션에 의한 다가전해질 복잡유체의 미세구조 특성 연구

Study on Microstructural Properties of Polyelectrolyte Complex Fluids by Employing Hybrid Molecular Simulations of Molecular Dynamics and Monte Carlo Scheme

이현수 전명석^†

Hyun Su Lee Myung-Suk Chun^†

한국과학기술연구원 복잡유체연구팀, 서울 130-650

Complex Fluids Team, Korea Institute of Science and Technology, Seoul 130-650, Korea

mschun@kist.re.kr

HWAHAK KONGHAK, October 2002, 40(5), 558-564(7), NONE

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Abstract

분자동력학(molecular dynamics)과 몬테카를로(Monte Carlo)의 혼성(hybrid) 알고리즘을 이용하여 harmonic spring 사슬과 하전된 단분자(monomer)들 사이의 Debye-Huckel potential로 표현된 다가전해질(polyelectrolyte)의 미세구조 특성을 규명하였다. Polyelectrolyte의 단일 사슬에 대해서 기존에 제안된 분자동력학과 몬테카를로의 혼성 알고리즘을 개선하여, polyelectrolyte의 conformation 특성인 끝단거리(end-to-end distance), 선회반경(radius of gyration), 그리고 구조인자(structure factor)를 한층 효율적으로 구할 수 있는 새로운 모사 기법을 개발하였다. 본 연구에서 새로이 개발된 알고리즘에 의한 모사 결과와 기존 문헌값과의 비교를 통해 해석 방법의 타당성과 정확성을 검증하였다. 끝단거리와 선회반경간 평균제곱의 비와 구조인자의 계산을 통해, polyelectrolyte 단분자의 하전율(change fraction)을 대변하는 Bjerrum length λB와 용액의 이온화세기에서 결정되어 용매의 screening 정도를 나타내는 Debye length k(-1)가 증가함에 따라 사슬이 신장되는 거동을 확인하였다.

The microstructural properties of charged polyelectrolytes described by a potential model regarding both the harmonic springs and Debye-Huckel interaction were investigated by employing a hybrid scheme of molecular dynamics(MD) and Monte Carlo(MC) simulations. Based on the previous hybrid scheme, a novel hybrid scheme has been developed in the present study, with which computational efforts are effectively reduced. We present the conformational properties such as end-to-end distance, radius of gyration and structure factor. It is evident that the simulation results of the present study agree well with the previously reported results. The elongation behavior of the polyelectrolyte chain can successfully be observed by the calculations of the characteristic mean square ratio of end-to-end distance to radius of gyration as well as the structure factor. As the Bjerrum length λB and the Debye length k(-1) increase, the polyelectrolyte chain becomes elongated.

Keywords

Molecular Dynamics Monte Carlo Simulation Polyelectrolyte Complex Fluid Structure Factor

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