使用密度泛函理論搭配隱式溶劑化模型計算Ca9(PO4)6團簇的相對穩定性

The relative stabilities of Ca9(PO4)6 clusters by density functional theory with implicit solvation model.

郭尚晨(Shang-Chen Guo)

指導教授 ： 林子仁

中原大學/工學院/化學工程研究所/碩士(2018年)

https://doi.org/10.6840/cycu201800835

摘要

在磷酸鈣團簇形成的過程中，檢測到了預成核團簇的存在，對於研究這些礦物質的早期成核過程，這些團簇的組成及結構是非常重要的資訊。這種團簇的大小不到一奈米，要經由實驗方法得到它們的結構訊息是不太容易的。在這次的研究中，使用了第一原理方法(Ab initio method)搭配隱式溶劑化模型(Implicit solvation model)研究中型磷酸鈣團簇的結構及紅外光譜。溶劑化效應增加了除了原本的緊湊結構之外，存在其他替代構型的可能性。鈣原子傾向於位在簇的外部以與水溶液環境中的水分子配位。還探討了中等Ca_9 〖(PO_4)〗_6團簇相對於波斯納團簇在水中的穩定性。在我們使用的方法中，都有找到穩定性比波斯納團簇(Posner’s cluster)高的結構，其幾何結構大多具有低對稱性或高偶極矩的特性。

關鍵字

磷酸鈣 ； 隱式溶劑化模型

並列摘要

During the formation of calcium phosphate clusters, the presence of pre-nucleation clusters was detected. The composition and structure of these clusters is very important information for studying the early nucleation process of these minerals. But their structural information has been difficult to determine because the size of these clusters are very small (less than 1 nm). In this study, we examined the structures and infrared spectra of medium-sized calcium phosphate clusters using ab initio calculations combined with implicit solvation models. The solvation effect increases the likelihood of other alternative configurations in addition to their compact configurations. Calcium atoms tend to be located outside of the cluster to coordinate with water molecules in the aqueous environment. The stability of medium Ca9(PO4)6 clusters relative to the Posner clusters in water was also discussed. We find structures with higher stability than Posner's clusters, and their geometry mostly has low symmetry or high dipole moment.

並列關鍵字

Calcium phosphate ； Implicit solvation model

參考文獻

Becke, A. D. (1993). Density-functional thermochemistry. III. The role of exact exchange. Journal of Chemical Physics, 98(7), 5648-5652.

Bots, P., Benning, L. G., Rodriguez-Blanco, J.-D., Roncal-Herrero, T., & Shaw, S. (2012). Mechanistic Insights into the Crystallization of Amorphous Calcium Carbonate (ACC). Crystal Growth & Design, 12(7), 3806-3814. doi: 10.1021/cg300676b

Boys, S. F. (1950). Electronic wave functions - I. A general method of calculation for the stationary states of any molecular system. Proceedings of the Royal Society of London A: Mathematical, Physical and Engineering Sciences., 200, 542-554. doi: 10.1098/rspa. 1950.0036

Cramer, C. J., & Truhlar, D. G. (2008). A universal approach to solvation modeling. Acc. Chem. Res., 41, 760-768.

Cramer, C. J., Truhlar, D. G., & Marenich, A. V. (2009). Universal Solvation Model Based on Solute Electron Density and on a Continuum Model of the Solvent Defined by the Bulk Dielectric Constant and Atomic Surface Tensions. J Phys Chem B, 113(18), 6378-6396.