稀土氟碳酸盐矿物的振动光谱研究

利用红外光谱、拉曼光谱和X射线能谱研究了四川冕宁氟碳铈矿和内蒙白云鄂博稀土矿区的黄河矿、氟碳钙铈矿、氟碳铈钡矿的谱学特征。结果表明,振动光谱是表征稀土氟碳酸盐矿物结构和组分特征的有效手段。CO32-离子的ν3红外谱带或ν1拉曼谱带的频率位置、谱带分裂状况和谱峰数目取决于矿物分子中的CO32-离子数目。而CO32-离子的ν2红外谱带或ν4红外和拉曼谱带的特征可区分稀土氟碳酸盐矿物、钡稀土氟碳酸盐矿物和钙稀土氟碳酸盐矿物。发现氟碳酸盐矿物中混有少量的重晶石。     

稀土氟碳酸盐矿物的拉曼光谱研究

研究了氟碳钡铈矿Ｃｅ２Ｂａ［ＣＯ３］３Ｆ２、氟碳钙铈矿Ｃｅ２Ｃａ［ＣＯ３］３Ｆ２和氟碳铈矿Ｃｅ［ＣＯ３］２Ｆ等矿物的拉曼光谱特征。结果表明,钡稀土氟碳酸盐矿物（氟碳钡铈矿、氟碳铈钡矿、黄河矿）的Ｒａｍａｎ光谱特点是,ν１和ν２为单峰值,ν３和ν４为双峰值。钙稀土氟碳酸盐矿物（氟碳钙铈矿）的拉曼光谱带中ν１和ν４为双峰值,ν２和ν３为单峰值。稀土氟碳酸盐矿物（氟碳铈矿）的Ｒａｍａｎ光谱的特点是,ν１、ν２和ν４为单峰值,ν３为双峰值。     

黄河矿的电子显微镜研究

黄河矿(BaCe(CO₃)₂F)是在我国发现的一种含钡-铈的氟碳酸盐新矿物,电子衍射方法测得晶体的六角晶胞参数α=5.07?,c=38.6?,后者比过去用X射线衍射方法所得结果大一倍,黄河矿是由轻重相差悬殊的原子组成的,文章讨论了用电子衍射方法研究这类矿物晶体结构的优越性。用晶格象方法观察到晶体结构沿c方向的堆垛层错,本文提出了形成这种层错的可能原因。 关键词：     

稀土氟碳酸盐矿物的光致发光谱和吸收谱研究

测定并讨论了产自四川冕宁矿区的氟碳铈矿和产自内蒙白云鄂博稀土矿区的黄河矿、氟碳钙铈矿、氟碳铈钡矿的光致发光谱。结果表明,稀土氟碳酸盐矿物在488.0nm和514.5nm激光激发下的光致发光中心是Nd3+,发光谱中的所有谱带均出自Nd3+的辐射跃迁。在488.0nm激光激发下,稀土氟碳酸盐矿物在495nm到733nm谱区的发光谱带强而尖锐,但在514.5nm激光激发下,这个谱区的谱带明显变弱或消失,转而出现783nm到907nm谱区的强发光谱带。可见光吸收谱表明稀土氟碳酸盐矿物对可见光的吸收也与矿物中的Nd3+有关。     

微区X射线能谱分析技术在研究钡-稀土氟碳酸盐矿物上的应用

本文就钡-稀土氟碳酸盐矿物的研究提出了一种简单的X射线能谱定量分析方法,对其可靠性作了检验。并指出,此法可能有助于今后发现这个系列矿物的新成员。 关键词：     

羟碳铈矿的高压拉曼光谱研究

羟碳铈矿是一种重要的含水稀土氟碳酸盐矿物,了解其高压下的物理性质对于探讨氟和水的存在对碳酸盐矿物物性的影响具有重要意义。运用金刚石压腔(DAC)技术与激光拉曼光谱,在室温下原位开展了羟碳铈矿的高压拉曼光谱学研究。结果显示,在常压下由[CO_3]~(2-)振动引起的拉曼峰共有6条:面内弯曲振动引起的拉曼峰位于604、742 cm~(-1),对称伸缩振动引起的拉曼峰位于1083、 1096和1103cm~(-1),而1430cm~(-1)属于非对称伸缩振动;由[OH]~–振动引起的拉曼峰有6条,分别位于3 174、3 197、3 290、3 345、3 526和3 648 cm~(-1)。随着压力的增加(0～30 GPa),未发现拉曼峰的消失或新拉曼峰的出现,表明在测试压力范围内羟碳铈矿未发生相变。拉曼峰均往高波数偏移,其位移与压力呈现良好的线性正相关关系,由[CO_3]~(2-)的面内弯曲振动引起的拉曼峰对压力的依赖系数最小,为2(0.06) cm~(-1)/GPa,而基团外振动引起的拉曼峰对压力的依赖系数最大,为4.2(0.11) cm~(-1)/GPa。对比无水碳酸盐高压下拉曼峰的位移,认为[OH]~–和F~–的存在导致羟碳铈矿高压下结构中[CO_3]~(2-)基团的振动模式对压力的依赖性发生变化,进一步影响到晶体高压下的各向异性。这为研究地球深部碳酸盐的高压物性行为提供了新的启示。     

黄河矿超结构的测定

黄河矿是在我国发现的一种钡铈氟碳酸盐新矿物,其理想化学式为BaCe[Fl(CO₃)₂],本矿物属三方晶系,利用四圆衍射仪收集强度数据,测得α=b=5.070(±0.003)?,c=38.408(±0.005)?,空间群为R3m. z=6,本文在前人工作的基础上,对该矿物进行了较为精确的测定,最后的偏离因子R=0.041。本文还对黄河矿赝结构及超结构的关系作了探讨,与前人工作进行了对比,对类似矿物的修正方案提出看法,对个别实验数据作了讨论。 关键词：     

黄河矿的晶体结构

黄河矿是在我国发现的一种新的钡铈氟碳酸盐矿物,化学式为BaCe(CO₃)₂F。根据单晶体X射线衍射资料,该晶体属赝三角晶系。晶胞参数α=5.1?;c=19.6?。空间群是C₃⁴-R3。每个晶胞含有三个化学式量。利用空间群的对称性及衍射强度测定了重原子的位置,并在此基础上结合晶体化学知识推断了轻原子的位置。本文讨论了由此得出的赝结构的可靠性,并就其特点与同类矿物的晶体结构作了比较。 关键词：     

油气微渗漏区蚀变矿物含量与光谱之间的定量分析

油气微渗漏的地表异常表现为：地表土壤的矿物组分异常和地表土壤的光谱异常,以中国的榆林地区为研究区,以在研究区内采集的119个样本的矿物组成及反射率光谱为研究数据,对油气微渗漏造成的地表蚀变矿物碳酸盐含量与其光谱吸收峰深度、宽度等特征参数进行了相关分析,建立并评价了测定碳酸盐含量的方法,提出了利用碳酸盐含量表征油气微渗漏程度的新方法。研究结果表明,该法不仅适于表征碳酸盐类油气微渗漏程度,也适用于对其他类型的蚀变矿物油气微渗漏程度的研究,因此可为利用高光谱遥感的光谱信息进行油气勘探的技术研究提供借鉴。     

钙长石质玉中钙铬榴石的谱学研究

所研究钙长石质玉中的绿色矿物是以钙铬榴石为主的石榴石,钙铬榴石在天然条件下非常稀有,颜色为翠绿色,品质高的钙铬榴石可与翡翠、祖母绿相媲美。前人对石榴石系列的其他端元矿物具有较为充分的研究,但对钙铬榴石的研究较少,且未见对钙长石质玉中钙铬榴石光谱特征的相关报道。使用JXA-8230电子探针确定样品石榴石平均组分为Uvt_49.66Grs_36.04Adr_13.58Pr_p0.67Sps_0.06,为以钙铬榴石为主的钙系石榴石。经Bruker Senterra R200L拉曼光谱仪测定样品拉曼位移为1 000,890,879,830,618,589,530,508,399,370,270,240和176 cm-1,受不同三价阳离子Cr3+,Al3+和Fe3+替代的相互影响而发生相应的偏移;用Bruker Vertex80红外光谱仪测定样品红外振动频率为1 019,951,908,844,826,721,669,608,538,496,462,430和413 cm-1,受不同组分晶胞体积及三价阳离子的质量分数影响,发生规律性振动偏移;通过Jasco MSV-5200显微紫外-可见光谱仪及近红外分光光度计测定样品,可见区Cr3+宽吸收带为439和613nm,存在453和685 nm吸收肩峰,同时可见Fe3+ 371 nm吸收肩峰,钙铬榴石主要致色离子为Cr3+。钙长石质玉中钙铬榴石的详细谱学研究为稀有钙铬榴石矿物的鉴定提供了丰富的谱学数据,为相似品独山玉进行区分奠定基础。     

Prediction of mineral crystal structures

The aim of our work has been to develop a computer simulation technique that can predict the structure of minerals. The basis of the technique is energy minimisation, i.e. all structural parameters are varied until the configuration with the lowest lattice energy is achieved; the initial configuration usually corresponds to an “ideal” structure based on regular polyhedra. The lattice energy is calculated using a specified potential model which includes electrostatic and short-range terms. These techniques can be applied to two distinct areas of structure prediction. The first concerns discrimination between alternative space groups proposed for the same structure. The second concerns the calculation of distortions from ideal close-packed structures. Here we concentrated mainly on silicate minerals. Furthermore, by varying the cell parameters we were able to simulate the effect of pressure on the crystal structure. Our results show that it is possible to establish potential models which predict detailed features of mineral structural chemistry.     

Molecular-dynamics calculation of the thermal conductivity coefficient of the germanium single crystal

The thermal conductivity coefficient of the germanium crystal lattice has been calculated by molecular dynamics simulation. Calculations have been performed for both the perfect crystal lattice and the crystal lattice with defects such as monovacancies. For the perfect germanium single crystal, the dependence of the thermal conductivity coefficient on the lattice temperature has been obtained in the temperature range of 150–1000 K. The thermal conductivity coefficient of the germanium lattice has been calculated as a function of the monovacancy concentration.     

The structure of titanium nickelide surface layers formed by pulsed electron-beam melting

X-ray structure analysis technique has been developed for a material heterogeneous over the depth. The structure of the TiNi intermetallide subjected to surface modification by an electron beam has been investigated. The following three layers differentiated in the microcrystalline structure have been singled out: (i) the external sharply textured layer 1–3 μm in thickness with a texture in the [100] B2 direction and a lattice periodicity parameter reduced by 1% in the direction of the normal, (ii) the intermediate gradient-stressed layer 10–15 μm in thickness with the texture of the initial ingot, and (iii) the original material. The crystal lattice of the surface as well as of the intermediate layer is in a state stretched along the surface and compressed along the normal to it. This lattice distortion is maximal in the surface layer and decreases towards the bulk of the material.     

Effects of wave propagation anisotropy on the wave focusing by negative refractive sonic crystal flat lenses

<正>In this study,wave propagation anisotropy in a triangular lattice crystal structure and its associated waveform shaping in a crystal structure are investigated theoretically.A directional variation in wave velocity inside a crystal structure is shown to cause bending wave envelcpes.The authors report that a triangular lattice sonic crystal possesses six numbers of a high symmetry direction,which leads to a wave convergence caused by wave velocity anisotropy inside the crystal.However,two of them are utilized mostly in wave focusing by an acoustic flat lens.Based on wave velocity anisotropy,the pseudo ideal imaging effect obtained in the second band of the flat lens is discussed.     

Growth,optical, mechanical and electrical studies of nonlinear optical crystal: l-Valinium oxalate

l-Valinium oxalate (LVO) single crystal has been grown by solution growth technique at room temperature. The crystal structure and lattice parameters were determined for the grown crystal by single crystal X-ray diffraction studies. Optical constants like band gap, refractive index, reflectance, extinction coefficient and electric susceptibility were determined from UV–vis–NIR spectrum. The microhardness studies reveal the mechanical strength of the grown crystal. The dielectric constant, dielectric loss and AC conductivity of the compound were calculated at different temperatures and frequencies to analyze the electrical properties. Nonlinear optical property was discussed to confirm the SHG efficiency of the grown crystal.     

Neutron scattering study of high-pressure phases obtained by thermobaric treatment

Abstract

A technique of thermobaric quenching has been developed at the Institute of Solid State Physics RAS, which made it possible to prepare and study bulk samples of high-pressure phases in a metastable state at ambient pressure. The paper briefly discusses results of recent neutron scattering investigations of the crystal structure and lattice dynamics of high-pressure phases and forms of various alloys and compounds, such as the bulk amorphous alloys Ga-Sb, GaSb-Ge, Zn-Sb, Al-Ge, amorphous ice and metal hydrides TiH, Mn-H, PdH and NiH.     

同步辐射光源在地球深部矿物研究中的应用

来自地球深部的矿物可能记录了地球形成和早期演化的历史，探索地球深部物质组成和它们形成的物理化学环境是一个十分前沿的科学问题．同步辐射X射线能量色散法对于解决微细矿物及包裹体矿物的晶体结构具有巨大的优势和潜力．在美国纽约长岛布鲁克海文国家实验室，利用同步辐射光源（Beamline X17C）和能量色散X射线衍射方法，开展了西藏铬铁矿中地幔深部矿物及中国大陆科学钻探钻孔岩心样品中地幔异常矿物的晶体结构分析，发现了一批新矿物种属和特殊的晶体结构，来自大陆科学钻探岩心样品的铁磷矿和西藏金刚石是两个例证．     

Large range of omni-directional reflection in 1D photonic crystal heterostructures

A simple design of one-dimensional omni-directional reflector based on photonic crystal heterostructures structure has been proposed. The proposed structure consists of a periodic array of alternate layers of SiO₂ and Te as the materials of low and high refractive indices, respectively. The structure considered here has three stacks of periodic structures having five layers each. The lattice period of successive stack is increased by a certain multiple (say gradual constant, δ) of the lattice period of the just preceding stack. For numerical computation, the method of transfer matrix method (TMM) has been employed. It is found that such a structure has wider reflection bands in comparison to a conventional dielectric PC structure and the width of the omni-directional reflection (ODR) bands can be enlarged by increasing the value of the gradual constant δ.     

Growth and characterization of organic nonlinear optical material: 5-Nitroindole (5NI) for optical applications

Single crystals of organic nonlinear optical material 5-Nitroindole (5NI) has been grown by slow cooling solution growth technique using methanol as a solvent. The grown crystal was subjected to single crystal X-ray diffraction technique to determine the lattice parameters. Fourier transform infrared spectrum (FTIR) was recorded to identify the presence of functional groups. The optical properties such as the optical band gap, extinction coefficient (k), refractive index (n) and optical conductivity (σ) were calculated. The optical band gap of 5NI is 2.33 eV. The melting point and thermal stability of the crystal was analyzed from TG/DTA studies. Dielectric studies were carried out at different temperatures and frequencies.