石墨烯纳米毛细管中方形冰形成的临界结晶压力的变化
Variation of Critical Crystallization Pressure for the Formation of Square Ice in Graphene Nanocapillaries
AI总结：
该研究通过全原子分子动力学模拟发现，石墨烯纳米毛细管中方冰形成的临界结晶压力随石墨烯尺寸增大而降低并趋近宏观值，尺寸过小则难以自发形成，且尺寸影响稳定性与结晶时间。
摘要：
室温下石墨烯纳米毛细管中的二维方形冰是一种引人入胜的现象，并已通过实验证实。与块体冰依赖于温度不同，高范德华压力成为诱导方形冰形成的最重要因素，需要进一步研究。通过对限制在两块平行石墨烯片之间的水进行全原子分子动力学模拟，并广泛改变石墨烯片的尺寸（长度和宽度），我们发现纳米毛细管中方冰形成的临界结晶压力强烈依赖于石墨烯片的尺寸。临界结晶压力随石墨烯尺寸增大而缓慢降低，并趋近于宏观结晶压力。通过估算实际压力，获得了石墨烯尺寸的不可冻结阈值，当石墨烯片小于该阈值时，实际上难以自发形成方形冰。此外，当石墨烯尺寸极小时，临界结晶压力会波动，且振荡范围随片尺寸增大而缩小，最终趋近于大片的单一临界结冰压力的宏观行为。石墨烯尺寸还影响方形冰的稳定性和结晶时间。
英文摘要：
Two-dimensional square ice in graphene nanocapillaries at room temperature is a fascinating phenomenon and has been confirmed experimentally. Instead of temperature for bulk ice, the high van der Waals pressure becomes an all-important factor to induce the formation of square ice and needs to be studied further. By all-atom molecular dynamics simulations of water confined between two parallel graphene sheets, which are changed in size (the length and the width of the graphene sheets) over a wide range, we find that the critical crystallization pressure for the formation of square ice in nanocapillary strongly depends on the size of the graphene sheet. The critical crystallization pressure slowly decreases as the graphene size increases, converging to approximately macroscopic crystallization pressure. The unfreezable threshold for graphene size is obtained by estimating the actual pressure and it is difficult to form the square ice spontaneously in practice when the graphene sheet is smaller than the threshold. Moreover, the critical crystallization pressure fluctuates when the graphene size is minuscule, and the range of oscillation narrows as the sheet size increases, converging to the macroscopic behavior of a single critical icing pressure for large sheets. The graphene size also affects the stability and crystallization time of square ice.
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