高压下D,L-扁桃酸结构相变的拉曼光谱研究

Raman Spectroscopic Study on High Pressure-induced Phase Transition of D,L-Mandelic

采用金刚石对顶砧高压装置,在室温下对D,L-扁桃酸(C8H8O3)进行了原位高压拉曼光谱研究,实验最高压力为2.2 GPa.结果表明,原来的一些拉曼峰在0.6 GPa左右突然消失或者劈裂,并同时出现了一些新的拉曼峰.通过进一步分析D,L-扁桃酸的拉曼频率随压力的变化,发现许多拉曼峰的移动在0.6 GPa时都出现了拐点.D,L-扁桃酸在0.6 GPa发生了由正交相(Pbca)到单斜相(P21/c)的压致结构相变.通过分析相变前后晶体结构及拉曼振动模式的变化,认为此压致结构相变是由高压下分子的密堆积效应和氢键结构的重新排列导致.完全卸压至常压后,卸压拉曼光谱与常压拉曼光谱一致,表明此压致相变可逆.

In situ Raman spectra of D,L-mandelic acid were characterized under high pressure generated by diamond anvil cell at room temperature. The pressure was up to 2. 2 GPa. Around 0.6 GPa, some original Raman peaks disappear or split, and some new Raman peaks emerge. Within the experimental pressure range, the curve of Raman frequence-pressure presented inflexions at 0.6 GPa, indicating a phase transition from Pbca to P21/c for D,L-mandelic acid has occurred at this pressure. On total release of pressure, the Raman spectra returns to its initial state, implying this transition is reversible.