高氯酸钠高压相变的拉曼光谱证据
Raman Evidences for Phase Transition of Sodium Perchlorate at High Pressure

何运鸿 ^1,2,3 田雨 ^1,2,3 赵慧芳 ^1,2,3 姜峰 ^1,2,3 谭大勇 ^1,2 肖万生 ^1,2 ^*

文摘	利用金刚石压腔高压装置,在0~20 GPa压力范围对高氯酸钠(NaClO_4)开展室温高压原位拉曼光谱测试,结合密度函数理论,计算NaClO_4几种可能结构的拉曼光谱,研究NaClO_4的压致相变现象,并确定其高压相晶体结构。实验结果显示:常温下硬石膏型结构的NaClO_4在约4 GPa时开始相变,在低压相ClO_4~-四面体内模振动ν_1(A_g)拉曼峰的低波数侧出现新峰,并在ν_2、ν_3、ν_4波数区出现多个新峰,反映高压相仍保持ClO_4~-四面体配位特征;如同NaClO_4低压相,高压相也未观察到离子间的晶格振动峰;相变在6.1 GPa时转变完全,直到最高实验压力19.5 GPa,也没有观察到进一步的相变现象。卸压过程中,于3.1 GPa开始从高压相转变成低压硬石膏相,1.7 GPa时相变完成。对比8.8 GPa实验观察的NaClO_4高压相拉曼光谱和理论计算的8.0 GPa时3种可能高压相(AgMnO_4型、重晶石型和独居石型)的拉曼光谱发现,实验观测结果与计算的独居石型结构基本一致,而与AgMnO_4型结构和重晶石型结构有明显差别。由此确定实验观察的NaClO_4高压相为独居石型结构,与相同结构的典型矿物硬石膏(CaSO_4)于2 GPa转变成独居石结构相一致。上述实验现象表明,NaClO_4在4 GPa左右发生可逆的重构型相变,与文献报道的NaClO_4于2 GPa左右转变成AgMnO_4型结构、于3 GPa左右进一步转变成重晶石型结构不一致,推测可能与他们的样品中含有少量水有关,或与高温高压实验环境有关,高压同时高温也许导致NaClO_4更复杂的变化。研究结果对于理解火星上广泛存在的高氯酸盐是否与火星内部火山作用相关,以及地球内部氯元素在板块俯冲、地幔柱等物质循环过程中的可能变化和作用有所助益。
其他语种文摘	Using a diamond anvil cell apparatus,we investigated the sodium perchlorate (NaClO_4) by Raman spectroscopy at pressure up to 20 GPa,and calculated the Raman spectra of anhydrite- (Cmcm),monazite- (P2_1/n),AgMnO_4- (P2_1/n),and barite-type (Pnma) structures of NaClO_4 by density function theory.The experimental data show that anhydrite-type NaClO_4 undergoes a structural transition at about 4 GPa.A new peak at lower Raman frequencies (975 cm~(-1)) than that of the ClO_4~- internal mode ν_1 (A_g) of the NaClO_4 ambient phase was obviously observed at 4.4 GPa.At the same time,several peaks at the corresponding wave numbers of the ClO_4~- internal modes (ν_2、ν_3、ν_4) arise.The phase transition is completed at about 6.1 GPa,and remains stable up to 19.5 GPa.The high pressure structure can be recovered at about 3.1 GPa in decompression.By comparison with the calculated Raman spectral profiles (at 8.0 GPa) of three potential high pressure structures,we infer that the high pressure phase has a monoclinic monazite-type structure.The pressure-induced phase transition of NaClO_4 is consistent with the anhydrite-monazite phase transition found in CaSO_4 at about 2 GPa.However,our finding appears inconsistency with the previous observations that the anhydrite-type NaClO_4 transforms to AgMnO_4-type at about 2 GPa and furthermore to the barite-type structure at around 3 GPa.The previous results could probably be influenced by the moisture of the sample combining with the high temperature and high pressure conditions.It may bring more complicated changes by simultaneous high pressure and high temperature environments.The research progress contributes to the understanding of not only the relationship between volcanic activity and the widespread distribution of perchlorate on Mars,but also the changes and functions of chlorine element during the recycles of subduction and mantle plume in the Earth's deep interior.
来源	高压物理学报 ,2018,32(4):041201-1-041201-9 【核心库】
DOI	10.11858/gywlxb.20180543
关键词	高氯酸钠 ; 高压 ; 拉曼光谱 ; 结构相变 ; 独居石型结构
地址	1. 中国科学院广州地球化学研究所, 中国科学院矿物学与成矿学重点实验室, 广东, 广州, 510640 2. 广东省矿物物理与材料研究开发重点实验室, 广东省矿物物理与材料研究开发重点实验室, 广东, 广州, 510640 3. 中国科学院大学, 北京, 100049
语种	中文
文献类型	研究性论文
ISSN	1000-5773
学科	物理学;地球物理学
基金	国家自然科学基金 ; 中国科学院战略性先导科技专项
文献收藏号	CSCD:6301718