Abstract:

In this paper, molecular dynamics was used to explore the effect of different temperatures and pressures on the crystallization process of water. The TIP4P/ICE four-point water model was used to build a three-layer (ice-water-ice) three-layer crystallization template. In the temperature part, molecular dynamics simulation was carried out under six temperature conditions, respectively. As the temperature of the box increased from 210 K to 250 K, the time of complete crystallization of the box was extended from 78 ns to 147 ns, and the density decreased. Therefore, as the temperature decreases and the degree of supercooling increases, the crystallization rate and the density of ice formation also increase. In the pressure part, the molecular dynamics simulation of the water crystallization process was carried out under six pressure conditions, respectively. It was found that with the increase of pressure, the crystallization time increased first and then decreased, and the crystallization time was the longest (115 ns) at 200 MPa. This was because the change of pressure would lead to the change of the freezing point of water. In addition, it was found that pressure has a direct effect on the water crystallization rate, and high pressure can directly promote the water crystallization. Ice forms were denser under high pressure.

Key words: water crystallization, molecular dynamics, food freezing

摘要：

利用分子动力学从微观角度探究不同温度、压力对水结晶过程的影响规律。模拟中采用TIP4P/ICE水模型，搭建冰-水-冰结晶模板。在温度部分，分别在六组温度工况下进行分子动力学模拟，随着盒子温度从210 K上升到250 K，盒子完全结晶的时间从78ns延长到147 ns，完全结晶后密度下降。因此，随着温度的降低以及过冷度的增加，结晶速度加快，形成冰的密度也增加。在压力部分，分别在六个压力工况下进行模拟，发现随着压力的升高，结晶时间先延长后缩短，在200 MPa时结晶时间最长（115 ns），这是由于压力的变化会导致水的冰点发生变化；压力对水结晶速度有着直接影响，高压力可以直接促进水结晶；高压下形成的冰的密度大于1000 kg/m³。

关键词: 水结晶, 分子动力学, 食品冷冻