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겹침 구형 세공 모델 내 Knudsen 확산에 관한 분자 전산 연구

Molecular Simulation Studies for Knudsen Diffusion in the Overlapping Sphere Pore Model

HWAHAK KONGHAK, August 1999, 37(4), 557-562(6), NONE
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Abstract

본 논문에서는 겹침 구형 세공 모델 내 비흡착적 Knudsen 분자의 동적 특성을 조사하기 위하여 molecular dynamaic 기법을 이용한 분자 전산 모사를 수행하였다. Knudsen 세공 확산 계수, 평균 충돌 시간, 세공 크기 분포도, velocity autocorrelation functions, mean-square displacement curves 등을 세공률 Ψ≥0.1 이상의 다양한 조건에서 게산 실측하고, 이를 문헌에 보고된 이론식들과 비교하여 이들 이론 예측식들이 가지는 유용성을 평가하였다. 단순 Boltamann 확산 이론식은 단지 높은 세공률 Ψ≥0.8의 조건에서 Knudsen 확산 계수가 일치하였으나, 반면 세공 분자와의 다중 충돌 효과를 고려한 동력학적 확장 이론식은 보다 낮은 세공률 Ψ≥0.3의 조건에서도 예측 적용성이 확장됨을 알 수 있었다. 한편, 본 전산 모사에서 얻어진 부차적인 결과는 이와 같은 세공 모델계의 분포 및 동적 효과에 관한 보다 세부적인 미시적 거동 특성을 분자 차원에서 설명하는데 이용되었다.
Molecular simulations using the molecular dynamaic method have been carried out to investigate the dynamic properties of the non-adsorbed Knudsen molecules in the overlapping sphere pore model. Knudsen pore diffusivities, mean collision times, pore-size distributions, velocity autocorrelation functions, mean-square displacement curves were computed over a wide range of porosity, Ψ≥0.1. Simulation data were used to assess the applicabilities of theoretical calculations reported in the literature. The simple Boltzmann approximation was found to be applicable only for the systems of higher porosity, Ψ≥0.8, whereas the extended kinetic equation based on multi-collisional density expansions has proven to be successful to predict Knudsen diffusivities in the range of Ψ≥0.3. The additional simulation results obtained in this work were used to elucidate detailed microscopic information on the distribution and dynamic effects of such pore systems at a molecular level.

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