Global phase diagrams for freezing in porous media
Global phase diagrams for freezing in porous media
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DOI：
10.1063/1.1426412
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发表时间：
2002-01
影响因子：
4.4
通讯作者：
R. Radhakrishnan;K. Gubbins;M. Śliwińska-Bartkowiak
中科院分区：
文献类型：
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作者：
R. Radhakrishnan;K. Gubbins;M. Śliwińska-Bartkowiak
使用分子模拟和自由能计算的基础上朗道理论，我们表明，冻结/熔化行为的流体的小分子在简单的几何形状的孔隙中可以理解的两个主要参数：孔隙宽度H* ~表示为流体分子的直径的倍数！以及测量流体-壁与流体-流体吸引相互作用的比率的参数α。α参数的值决定了冻结行为的定性性质，例如，冻结温度的变化方向和新相的存在或不存在。对于狭缝形孔，较大的a值导致受限流体的冻结温度增加，并且导致六方相的存在。对于容纳三层或多层吸附物分子的孔隙，有几种接触层相~非均匀相，其中接触层具有与内层不同的结构！被观察到。较小的a值导致冷冻温度降低。参数H* 决定了冻结温度的变化幅度，并且还可以影响一些新相的存在。结果表示为对于特定孔宽度的转变温度与α的曲线图。实验结果也提出了各种吸附物在活性炭纤维~ACF！覆盖宽范围的a值; ACF具有平均孔宽为1.2nm的狭缝形孔。实验和仿真结果表明定性协议。© 2002年美国物理研究所。@DOI：10.1063/1.1426412#
Using molecular simulations and free energy calculations based on Landau theory, we show that freezing/melting behavior of fluids of small molecules in pores of simple geometry can be understood in terms of two main parameters: the pore width H* ~expressed as a multiple of the diameter of the fluid molecule ! and a parameter a that measures the ratio of the fluid-wall to the fluid‐fluid attractive interaction. The value of the a parameter determines the qualitative nature of the freezing behavior, for example, the direction of change in the freezing temperature and the presence or absence of new phases. For slit-shaped pores, larger a values lead to an increase in the freezing temperature of the confined fluid, and to the presence of a hexatic phase. For pores that accommodate three or more layers of adsorbate molecules several kinds of contact layer phase ~inhomogeneous phases in which the contact layer has a different structure than the inner layers! are observed. Smaller a values lead to a decrease in the freezing temperature. The parameter H* determines the magnitude of shift in the freezing temperature, and can also affect the presence of some of the new phases. Results are presented as plots of transition temperature vs a for a particular pore width. Experimental results are also presented for a variety of adsorbates in activated carbon fibers~ACF! covering a wide range of a values; the ACF have slit-shaped pores with average pore width 1.2 nm. The experimental and simulation results show qualitative agreement. © 2002 American Institute of Physics. @DOI: 10.1063/1.1426412#