大氣中微粒的吸濕性成長率對於大氣輻射傳遞及氣候預報有著重要的效應，而海鹽中的氯化鈉亦為 大氣奈米微粒的主要組成之一，其尺寸大多小於100奈米。由於藉實驗量測小於40奈米的微粒的吸濕 性行為，需克服尺寸效應與雜質影響等問題，因此本研究嘗試以分子動力學模擬技術，初步研究探討氯 化鈉吸濕性的行為。在設定合適的參數與勢能函數與力場後，依序進行三組模擬實驗。在氯化鈉引進空 隙結構分析中，發現空隙愈多，固態晶體的結構愈不容易维持長程有序的現象。而在氯化鈉雙表面吸附 實驗，模擬結果顯示空隙愈多，對於吸附水分子的效果愈好，說明晶體表面具有一定的空隙量將有利於 溶液的吸濕性成長。最後的氯化鈉團簇吸附實驗模擬，能說明大氣中凝結核吸附水分子行為，其結果顯 示當水分子質量比大於40.5%時，第一層水分子幾乎已完全包覆氯化鈉團簇，且有更多的水分子凝結在 第一層水分子之上。因此藉由分子動力學模式之模擬，有助於完整描述溶液的成長過程。

The hydroscopic growth of atmospheric particles has important consequences for the atmospheric radiative transfer of aerosols and climate prediction. Sodium chloride (NaCl) nanoparticles from sea salt comprise a major component of atmospheric aerosols. The size range below 100 nm was found to dominate sea-salt number. Experimental observations of the growth factors at sizes smaller than 40 nm are limited by difficulties in the size effect and impurity concerns. Therefore, the study examines the process that water molecular is absorbed by sodium chloride by applying molecular dynamic simulation. The crystal surface of sodium chloride is introduced defects. Three simulation experiments were carried out with setting suitable parameters of the potential function and force field. For the experiment of introducing defects on the surface of sodium chloride, the result shows that the more the introduced defect, the more difficult the solid crystal maintains the long-range orientational order. The result from the experiment simulating the double surface absorption process of sodium chloride shows that the more the defect introduced, the better the effect for adsorbing water molecules. It indicates that the absorption is evident at where the defects are introduced. The last experiment is the sodium chloride cluster adsorption simulation, which is regarded as the experiment that can describe the hydroscopic behavior of aerosols in the real atmosphere. When the mass ratio of water molecule is larger than 40.5%, the first layer of water molecules have almost completely coated sodium clusters, and more water molecules consistently condense on the first layer of water molecules. Therefore, the molecular dynamic simulation is helpful for completely examine the growth of solution.