Molecular dynamics study of swelling patterns of Na/Cs-montmorillonites and hydration of interlayer cations

doi:10.1088/1674-1056/22/2/027103

摘要/Abstract

摘要： We report on a molecular dynamics study of swelling patterns of an Na-rich/Cs-poor montomorillonite and a Cs-montomorillonite. The recently developed CLAYFF force field is used to predict the basal spacing as a function of the water content in the interlayer. The simulations reproduce the swelling patterns of the Na and Cs-montomorillonite, suggesting a mechanism of its hydration different from that of the montomorillonite. In the meanwhile, we find that the differences in size and hydration energy of Na and Cs ions have strong implications for the structure and the internal energy of interlayer water. In particular, our results indicate that the hydrate difference in the presence of coexistent Na and Cs has a larger influence on the behavior of clay-water system. For Na-rich/Cs-poor montomorillonite, the hydration energy values of Na ions and water molecules each have a dramatic increase compared with those in Na-montomorillonite on the interlayer spacing, and the hydration energy values of Cs ions and water molecules decrease somewhat compared with those in Cs-montomorillonite.

关键词: montmorillonite, molecular dynamics simulation, swelling, hydration energy

Abstract: We report on a molecular dynamics study of swelling patterns of an Na-rich/Cs-poor montomorillonite and a Cs-montomorillonite. The recently developed CLAYFF force field is used to predict the basal spacing as a function of the water content in the interlayer. The simulations reproduce the swelling patterns of the Na and Cs-montomorillonite, suggesting a mechanism of its hydration different from that of the montomorillonite. In the meanwhile, we find that the differences in size and hydration energy of Na and Cs ions have strong implications for the structure and the internal energy of interlayer water. In particular, our results indicate that the hydrate difference in the presence of coexistent Na and Cs has a larger influence on the behavior of clay-water system. For Na-rich/Cs-poor montomorillonite, the hydration energy values of Na ions and water molecules each have a dramatic increase compared with those in Na-montomorillonite on the interlayer spacing, and the hydration energy values of Cs ions and water molecules decrease somewhat compared with those in Cs-montomorillonite.

Key words: montmorillonite, molecular dynamics simulation, swelling, hydration energy

中图分类号: (Molecular dynamics calculations (Car-Parrinello) and other numerical simulations)

71.15.Pd

刘涛, 陈雨青. Molecular dynamics study of swelling patterns of Na/Cs-montmorillonites and hydration of interlayer cations[J]. 中国物理B, 2013, 22(2): 27103-027103.

Liu Tao (刘涛), Chen Yu-Qing (陈雨青). Molecular dynamics study of swelling patterns of Na/Cs-montmorillonites and hydration of interlayer cations[J]. Chin. Phys. B, 2013, 22(2): 27103-027103.

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