自適應力匹配法開發的力場研究:模擬超臨界二氧化碳的結構和傳輸性質

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2019

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隨著世界各國的工業發展,二氧化碳被廣泛地排放至我們的大氣中。重新利用二氧化碳是維持地球上生活環境的關鍵課題之一。二氧化碳也是在生物、化學或地球科學領域中的重要流體,特別是超臨界二氧化碳(sCO2)已經應用於許多工業合成的應用中,有良好的選擇性來提取有價值的產物。因此了解sCO2的傳輸和結構性質可以幫助科學家提高工業上sCO2的使用效率。 從2005年到現在,已經發表了許多組的CO2力場參數,這些參數可用於分子動力學模擬(MD)對sCO2進行理論建模。但可惜的是,它們都沒有辦法在模擬中完全呈現sCO2的物理或化學性質。因此為了想要能描述在超臨界情況下的CO2與其他溶質的交互作用,在新的力場參數開發中仍然面臨了許多的挑戰。 自適應力匹配法(AFMM),可以用ab initio 級別所計算出的力,來擬合MD的力場參數,目前已經被證明可以有效地對超臨界流體的力場進行改善。在這項工作中,我們將會利用透過AFMM而獲得的新CO2力場參數,並使用MD模擬計算CO2的自擴散係數、徑向分佈函數和痕量擴散,最後將與文獻結果和實驗數據進行比較分析,來驗證新力場參數表現sCO2傳輸和物理性質的能力。
Due to the industrial evolution, carbon dioxide is a widely emitted to our atmosphere. Re-utilizing CO2 becomes an important and critical issue for maintain a sustainable living environment on earth. CO2 is also an important fluid in biological, chemical, or geochemical processes. In particular, supercritical carbon dioxide (sCO2) has been applied in numerous industrial synthesis applications for selectively extracting valuable product. Understanding the transport and structural properties of sCO2 can help the scientists improve the efficiency of the industrial extraction processes. Since 2005, there are several theoretical modeling studies in sCO2 using molecular dynamics simulations (MD). Although there are multiple sets of CO2 force field parameters reported in the literature, none of them can fully present the physical properties of sCO2 in simulation. It still poses the challenge in force field parameter development for describing the sCO2–solute interactions under the supercritical CO2 condition. Adaptive force matching method (AFMM), fitting the force fields from ab initio MD, has been proven to parametrize force fields effectively for supercritical liquid. In this work, we present the new parameters obtained by AFMM and using MD simulation to calculate the self-diffusion coefficient, radial distribution functions and trace-diffusion then compare with literature results and experiment data to advance the force field parameters for sCO2.

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超臨界二氧化碳, 分子力場, 自適應力匹配法, 第一原理, Supercritical Carbon Dioxide, Force Field, Adaptive Force Matching

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