常温高压下水的液-液相变

Liquid-Liquid Phase Transition of Water at High Pressure and Ambient Temperature

在300K、0．1～1400MPa条件下，利用碳化硅压腔，进行了液态水的拉曼光谱测量和研究。实验结果表明：随着压力的增大，水的对称伸缩振动峰（v。）整体向低频方向移动，但在约200和620MPa处存在不连续，可明显分为3个区间（Ⅰ、Ⅱ、Ⅲ）；水从状态I到状态Ⅱ再到状态Ⅲ，其拉曼位移对压力P的变化率（fdv1／dpf）减小，表明水变得越来越难以压缩；随着压力的改变，相邻的五水分子聚合体之间的连接方式发生了变化。这些性质表明，液态水在约200和620MPa处可能存在着液一液相转变。

In-situ Raman measurement of water has been conducted at the temperature of 300 K and the pressure of 0.1-1 400 MPa using a SiC anvil cell. The experimental results show that the frequency of liquid water vl decreases with increase of pressure （p）,and two discontinuities are observed at about 200 and 620 MPa. Therefore three states of water are recognized. From state [ to state II then to state III,the value of L dvt/dpl reduces,indicating that the compressibility is related to the pressure, and it is becoming more difficult to compress as the pressure is increasing. The connection mode of a water molecule with its neighboring water molecules changes as the pressure increases. The discontin- uous property of water suggests a possible liquid to liquid phase transition and structural change at 200 and 620 MPa.