锗酸盐晶体压致非晶化的研究

高压拉曼散射研究表明．ＣｕＧｅＯ３，Ｌｉ２ＧｅＯ３和Ｌｉ６Ｇｅ２Ｏ７三种晶体分别在７，１２和１１ＧＰａ压力下转变为非晶。在高于起始转变压力以上一定范围压致非晶是可逆的，ＣｕＧｅＯ３，Ｌｉ２ＧｅＯ３和Ｌｉ６Ｇｅ２Ｏ７压致非晶的不可逆转变压力分别为１４．１，２０和２０ＧＰａ。压致非晶ＣｕＧｅＯ３的重新晶化温度在６００℃附近。锗酸及系列晶体的压致非晶化与它们的成份和结构有关，随着在这一系列晶体中Ｌｉ２Ｏ含量的增加，压致非晶化的压力趋于减小。     

晶体压致非晶化的拉曼散射研究

本文主要介绍压致非晶化研究的进展，其中包括我们对β—ＢａＢ＿２Ｏ＿４，ＬｉＢ＿３Ｏ＿５，Ｐｂ＿５Ｇｅ＿３Ｏ＿１１和Ｌｉ＿２Ｇｅ＿７Ｏ＿（１５）的拉曼散射研究结果。综述了压致非晶的结构特征，压致非晶转变机制和重新晶化过程。     

Bi2Ti4－xTexO11的合成及相变研究

本文合成了系列Ｂｉ２Ｔｉ４－ｘＴｅｘＯ１１样品，拉曼光谱及Ｘ射线衍射谱表明该体系的相转化边界发生在ｘ＝０．５处，Ｂｉ２Ｔｅ４Ｏ１１的压致结构相变的压力为８．２ＧＰａ。本文结果证实了我们过去对Ｂｉ２Ｔｉ４Ｏ１１相变提出的机制     

Bi2Ti4－xTexO11的合成及相变研究

本文合成了系列Ｂｉ２Ｔｉ４－ｘＴｅｘＯ１１样品，拉曼光谱及Ｘ射线衍射谱表明该体系的相转化边界发生在ｘ＝０．５处，Ｂｉ２Ｔｅ４Ｏ１１的压致结构相变的压力为８．２ＧＰａ。本文结果证实了我们过去对Ｂｉ２Ｔｉ４Ｏ１１相变提出的机制     

三硼酸铯和硼酸铯锂晶体的晶格振动光谱研究

本文对新型非线性光学晶体三硼酸铯（ＣｓＢ３Ｏ５∶ＣＢＯ）和硼酸铯锂（ＣｓＬｉＢ６Ｏ１０∶ＣＬＢＯ）进行了晶格振动光谱研究。首先对两种晶体的基本晶格振动模进行了对称性分类,记录了两种晶体低温下的拉曼光谱和室温下的红外反射光谱,对晶体的晶格振动模进行了认定,将振动模归属于平面六元环（Ｂ３Ｏ６）和四面体（ＢＯ４）。然后比较了ＣＢＯ,ＣＬＢＯ和ＬＢＯ（ＬｉＢ３Ｏ５）三种晶体的晶格振动光谱,讨论了阳离子对振动光谱的影响。另外,还讨论了硼酸盐晶体晶格振动模ＬＯ ＴＯ分裂的大小与晶体非线性光学系数之间的关系。     

KH_2PO_4和（CH_3NHCH_2COOH）_3CaCl_2在高压下的状

在活塞圆筒式Ｐ～Ｖ关系测量装置上，研究了ＫＨ＿２ＰＯ＿４（ＫＤＰ）和（ＣＨ＿３ＮＨＣＨ＿２ＣＯ－ＯＨ）＿３ＣａＣＩ＿２［Ｔｒｉｓ－ｓａｒｃｏｓｉｎｅｃａｌｃｉｕｍｃｈｌｏｒｉｄｅ（ＴＳＣＣ）］在室温下、４．５ＧＰａ内的ｐ～Ｖ关系。实验结果表明：ＫＤＰ在２．１ＧＰａ左右有一个相变；ＴＳＣＣ在０．８ＧＰａ和３．２ＧＰａ左右各有一个相变。本工作还给出了它们在相变前后的状态方程，以及它们的格临爱森参数γＯ、体积模量Ｂ＿ｏ和Ｂ＿ｏ的压力导数Ｂ＿ｏ。     

γ－Fe_2SiO_4在静水压下的压缩行为的测定

采用同步辐射高压原位Ｘ光衍射技术及金刚石对顶压砧高压装置，对γ－Ｆｅ＿２ＳｉＯ＿４进行了静水压条件下等温压缩行为的测定，最高压力达２３ＧＰａ。γ－Ｆｅ＿２ｓｉＯ＿４在０～２３ＧＰａ压力范围内的ｐ、Ｖ数据表明，其等温压缩可分为两个阶段：若设Ｋ＇＿０＝４，在０～１８Ｇｐａ，Ｋ＿０＝１８９±２ＧＰａ；而在１８～２３０Ｐａ，Ｋ＿０＝２１３±２ＧＰａ。我们认为，样品在１８ＧＰａ以下处于较好的静水压状态，压力超过１８ＧＰａ，传压介质的静水压性质变坏，所以Ｋ＿０值偏高。在整个实验过程中并未发现样品有任何发生相变的迹象。最后，对一些虽然使用了液体介质但得不到静水压条件的实验现象进行了讨论。     

二硼酸锂晶体的压致非晶化研究

二硼酸锂晶体的压致非晶化研究李玉栋，扈士芬，蓝国祥（南开大学物理系天津３０００７１）Ｐｒｅｓｓｕｒｅ－ＩｎｄｕｃｅｄＡｍｏｒｐｈｉｓａｔｉｏｎｏｆＬｉｔｈｉｕｍＤｉｂｏｒｉｔｅ￥ＹｕｄｏｎｇＬｉ；ＳｈｉｆｅｎＨｕａｎｄＧｕｏｘｉａｎｇＬａｎ（Ｄｅｐａ...     

非晶态（Fe＿（1－x）Co＿x）＿（77．5）Nd＿4B＿（18．5）合金的电阻率的压力系数和压力弛豫研究

在０．０００１－２．４ＧＰａ流体静压力范围详细研究了非晶（Ｆｅ＿ｘＣｏ＿ｘ）＿（７７．５）Ｎｄ＿４Ｂ＿（１８．５）（０≤ｘ≤１．０）合金的电阻率与压力的关系，得到该非晶合金电阻率的压力系数随组分ｘ变化的规律。结果表明：用少量的钴（ｘ＝０．２）替代铁，不会影响其硬磁性和热稳定性，同时却可减小电阻率的压力系数，从而增强电磁性能在压力下的稳定性。此外还观测到在０．５１ＧＰａ保压３－２４ｂ的结构弛豫，进一步求出该非晶台金电阻率的压力弛豫时间对组分ｘ的依赖关系。     

α-quartz型GeO2高压相变的分子动力学研究

采用在经典离子晶体作用势中附加Ｍｏｒｓｅ势,并进行必要的量子化修正,对α－ｑｕａｒｔｚ型ＧｅＯ２结构随压力变化特性,进行分子动力学计算模拟,获得了在压力高于６．０ＧＰａ,α－型ＧｅＯ２从晶相向非晶相相变的模拟结果,并利用其摩尔体积变化,键角、径向分布１、配位数等重要信息对模拟结果作了深入的探讨,相变后的非晶相,由占体积６６％的八面体结构和３３％的四面体结构组成的非晶体,其中还有极少量的α－ｑｕａｒｔｚ型ＧｅＯ２存在。     

High pressure study of acetophenone azine

High pressure Raman spectra of acetophenone azine (APA) have been measured up to 17.7 GPa with a diamond anvil cell. Two crystalline-to-crystalline phase transformations are found at pressures about 3.6 and 5.8 GPa. A disappearance of external modes and the C–H vibration at pressures higher than 8.7 GPa suggests that the sample undergoes a phase transition to amorphous or orientationally disordered (plastic) state, and the amorphization was completed at about 12.1 GPa. The disordered state is unstable and, then, a polymerization transformation reaction occurs with a further pressure increase. After the pressure has been released, the polymerization state can remain at the ambient condition, indicating that the virgin crystalline state is not recovered. The results show that the phenomenon underlying the pressure induced phase transition of APA may involve profound changes in the coordination environments of the symmetric aromatic azine.     

Structural stability of tin clathrates under high pressure

High pressure Raman scattering experiments have been performed for Rb₈Sn₄₄□₂ in order to investigate the pressure induced phase transition. At pressures of 6.0 and 7.5 GPa, Raman spectrum was drastically changed, indicating the phase transitions. The irreversibility of the spectral change and the disappearance of Raman peak observed at 7.5 GPa strongly suggest the occurrence of irreversible amorphization.     

In situ Raman and photoluminescence study on pressure‐induced phase transition in C60 nanotubes

Single crystalline C₆₀ nanotubes having face‐centered‐cubic structure with diameters in the nanometer range were synthesized by a solution method. In situ Raman and photoluminescence spectroscopy under high pressure were employed to study the structural stabilities and transitions of the pristine C₆₀ nanotubes. A phase transition, probably because of the orientational ordering of C₆₀ molecules, from face‐centered‐cubic structure to simple cubic structure occurred at the pressure between 1.46 and 2.26 GPa. At above 20.41 GPa, the Raman spectrum became very diffuse and lost its fine structure in all wavenumber regions, and only two broad and asymmetry peaks initially centered at 1469 and 1570 cm^–1 were observed, indicating an occurrence of amorphization. This amorphous phase remained to be reversible until 31.1 GPa, and it became irreversible to the ambient pressure after the pressure cycle of 34.3 GPa was applied. Copyright © 2012 John Wiley & Sons, Ltd.     

Structure of alkali borate glasses at high pressure: B and Li K-edge inelastic X-ray scattering study

We report the first in situ boron K-edge inelastic x-ray scattering (IXS) spectra for alkali borate glasses (Li2B4O7) at high pressure up to 30 GPa where pressure-induced coordination transformation from three-coordinated to four-coordinated boron was directly probed. Coordination transformation (reversible upon decompression) begins around 5 GPa and the fraction of four-coordinated boron increases with pressure from about 50% (at 1 atm) to more than 95% (at 30 GPa) with multiple densification mechanisms, evidenced by three distinct pressure ranges for (d[4]B/dP)T. The lithium K-edge IXS spectrum for Li-borate glasses at 5 GPa shows IXS features similar to that at 1 atm, suggesting that the Li environment does not change much with pressure up to 5 GPa. These results provide improved understanding of the structure of low-z glass at high pressure.     

Sr2Bi4Ti5O18的压致结构相变

 使用4∶1的甲醇-乙醇混合液作传压介质，利用金刚石对顶砧装置（DAC），研究了层状铁电体Sr₂Bi₄Ti₅O₁₈的在位高压拉曼光谱和压致结构相变（0～27 GPa）。发现在8.31 GPa，Sr₂Bi₄Ti₅O₁₈经历了一次结构相交。在23.13 GPa以上，Sr₂Bi₄Ti₅O₁₈似乎出现了压致非晶相交的先兆。并使用内模方法对Sr₂Bi₄Ti₅O₁₈的内模进行了指认。     

High pressure investigations on amorphous selenium

We report the diamond anvil cell (DAC) high pressure powder X-ray diffraction studies on amorphous selenium (a-Se) under truly hydrostatic pressure condition up to 20 GPa. Amorphous selenium exhibits a sharp and irreversible transition to a hexagonal structure at 10.6 ± 0.1 GPa. It is also known that metallization occurs in a-Se around this pressure. Some plausible arguments are provided to suggest that the amorphous to crystalline transition may be driven by metallization.     

高压诱致的反式联苯乙烯酮结构相变与化学反应

 利用金刚石对顶砧（DAC）高压装置在室温下对反式联苯乙烯酮（Trans, Trans-Dibenzylideneacetone）分子晶体进行了高压拉曼谱、荧光光谱和能量色散X射线衍射（EDXRD）研究。结果表明,在压力为1.0~1.3 GPa时,反式联苯乙烯酮发生了晶体—晶体的结构相变,同时开始伴随有压力诱导的化学反应,反应完成的压力为6.5 GPa。高压X射线研究表明,这次相变有新的共价键产生,可能的化学变化过程是,C＝C双键打开再与相邻的分子结合生成新的共价键。在压力大约为11 GPa时,反式联苯乙烯酮分子晶体再次发生了晶体的结构相变。新产生的物质在卸压后依然保持稳定。