矿物中的色心:以金刚石氮心为例

色心是矿物颜色的主要形成机制之一,含色心的矿物有钾盐、石盐、萤石、石英和金刚石等.本文主要介绍金刚石中的色心,金刚石中有众多的缺陷,特别是其中的氮心.氮心由一个置换碳的氮和一个空位组成,包括电中性的NV0和带负电的NV-,NV-心可以用作室温量子比特.本文叙述了NV-心的结晶构造和电子结构,以及通过NV-心的光致发光、电子自旋和核自旋一步步地建立电子和核的量子比特.最后,讨论了氮心在量子信息、传感器和生命科学等领域的应用前景.     

辐射处理金刚石的谱学研究及其意义

利用傅立叶显微红外光谱、紫外-可见-近红外吸收光谱、低温光致发光谱、拉曼光谱等4种谱学方法,对10颗辐照改色（R1-R10）的彩色天然金刚石进行了研究。利用可见吸收光谱和低温光致发光谱研究了金刚石石中的点缺陷产生系列的色心峰,指出在可见吸收光谱中除了有N3心吸收峰外,还可见595和637色心峰;在低温光致发光谱中发现有色心组合峰575,595和637等的出现,此组合峰与近红外区4929cm^-1处的H1b和5156cm^-1处的H1C色心峰共同存时,不仅是辐照处理绿色金刚石的鉴定证据,也是辐照处理各种彩色金刚石的重要的标志之一。本研究为辐射处理金刚石的鉴别和工艺流程提供了新的谱学依据和思路。     

金刚石呈色机制的新观点

已知金刚石中能产生颜色的点缺陷(即色心)主要有氮、硼、空穴、填隙子以及各种形式的氮与空穴的复合体。随着各种现代微束与谱学分析技术以及量子化学计算的应用，对金刚石晶格中氮、硼以外的杂质—氢与过渡金属离子的赋存状态的研究，我们发现了新的致色点缺陷：成键氢，镍、钴离子，及其与氮的复合体，从而形成了氢致色与过渡金属离子致色的金刚石呈色机制的新观点。     

湖南发现天然产出的Ⅰb型金刚石

正金刚石结构是由两个面心立方点阵沿立方晶胞的体对角线偏移1/4单位嵌套而成的晶体结构。按N含量和N聚集类型,金刚石一般分为Ⅰa型、Ⅰb型、Ⅱa型和Ⅱb型(含B元素)。研究证实,金刚石形成时杂质N主要以孤N(C中心)形式存在,在一定条件下,孤N逐渐转变为双原子N(A中心),这一转变过程所需时间较短,因而在自然界中Ⅰb型金刚石较少见。Ⅰb型金刚石以孤原子氮的存在形式被作为合成金刚石的证据。目前,华北和扬子地区金刚石矿产调查二级项目组在湖南发现了8粒Ⅰb型金刚石,     

基于红外光谱-拉曼光谱研究山东郯城砂矿的金刚石及包裹体类型

对山东郯城砂矿中的金刚石开展了傅里叶红外光谱和显微激光拉曼光谱的测试,结果显示,红外光谱均可见C—C的本征峰;绝大多数可见氮的吸收峰:双氮的吸收峰、聚合氮的吸收峰和氮片晶的吸收峰;部分可见氢的吸收峰:C—H的吸收峰、C—N的吸收峰和H2O的吸收峰.郯城金刚石以Ⅰa型金刚石为主,有ⅠaA、ⅠaB、ⅠaAB型,而Ⅱa型仅1粒;氮类型包括双氮(A心)、聚合氮(B心)及氮片晶(B'心),说明金刚石中的孤氮(C心)已经转化为双原子氮,但部分双原子氮未完成进一步的聚形.金刚石拉曼峰值集中在1131 cm–1,拉曼位移漂移程度较小,说明金刚石内部应力发生小幅的变化.在郯城金刚石中首次发现柯石英包裹体,出现139 cm–1、152 cm–1、212 cm–1、272 cm–1、328 cm–1、356 cm–1、428 cm–1和529 cm–1左右的拉曼峰值.在1粒金刚石中柯石英包裹体数量多达十余个,直径几μm至几十μm,呈针状、哑铃状、浑圆状和短柱状等多种形态.郯城金刚石中柯石英包裹体的出现,可作为郯城地区存在榴辉岩型金刚石的可靠标志,也佐证了该地部分金刚石的来源可能和洋壳循环或者俯冲过程有关.镁橄榄石包裹体上覆分散的黑色石墨斑点,与山东蒙阴、辽宁和湖南金刚石中的镁橄榄石等不同种类包裹体具有相似特征,推测这些石墨斑点是晶体包裹体形成后,由于外部环境温压条件的变化产生.     

金刚石的微区显微红外光谱分析及其意义

金刚石的微区显微红外光谱分析表明：金刚石的形成是一个结晶物化条件变异，原始物质变换的复杂而又漫长的过程；杂质N、H等在其中的分布不均匀；同一晶体的中心部位其氮聚合态的转变时间与边缘相差约602Ma；金刚石中的成键氢以对应－CH3的C－H键形式存在要比对应于＞C＝CH2的C－H键形式存在更为广泛。利用红外光谱研究晶化固态物质必须强调定向及微区研究的意义。     

华北克拉通南缘碱性基性岩金刚石成因探讨——来自红外光谱的证据

我国最主要的金刚石产地均位于华北克拉通。目前在华北克拉通苏皖北部的碱性基性岩中发现大量的微粒金刚石，经确认这是一种不同于母岩为金伯利岩和钾镁煌斑岩的新类型金刚石。本文利用傅里叶可变红外光谱对这些金刚石进行测试和分析。研究结果表明，大多数金刚石中包含单原子氮（C心），少部分包含双原子氮（A心）和聚集氮（B心），其中Y心（1145~1150cm-1）与C心伴生，指示了这些金刚石大多为天然的Ib型、Ib/IaA型和IaAB型，其中以Ib型为主。N元素是金刚石中最常见的与晶格缺陷有关的杂质。该地区出土的金刚石N的含量普遍不高，通过对其中IaAB型金刚石的计算，认为该区IaAB型金刚石在地幔中赋存时间为550Ma左右，温度在1225℃左右，相当于地下150km深度。而大量Ib型金刚石的出现，说明在金刚石的初生阶段就被带出稳定区域。导致了N元素没有发生向A心的转化。     

津巴布韦天然立方体与八面体镶嵌结构金刚石中氮、氢缺陷择优取向

天然金刚石形成于地球深部,反映丰富的地幔信息及演变历史[1-2]。金刚石中特征的氮原子缺陷是追溯其地幔存留时间和保存温度的重要依据[3-4],氮缺陷近年来也被认为是实现量子计算的优良载体,成为炙手可热的研究热点[5-6]。本世纪初新发现的储量巨大的津巴布韦砂矿型天然金刚石,引起了国内外学者的极大关注[7-10]。我们对已获得的津巴布韦金刚石样品进行预研究,注意到该产地金刚石具有特殊的立方体-八面体同时发育的镶嵌结构(下文简称mixed-habit),其氮和氢含量丰富,且氮和氢分别沿八面体生长区{111}和立方体生长区{100}具有择优取向特点。这种mixed-habit结构,不同于传统天然金刚石以八面体生长为主的结构[11],而与高温高压(HPHT)合成金刚石的结构较为相似[12],因而具有特殊的地质学背景和研究意义。我们将在下一阶段对这类金刚石在不同生长方向氮和氢缺陷存在形式及分布规律进行深入定量研究。重点通过电子顺磁共振光谱(EPR)对于不同氮缺陷如孤氮、双氮等的浓度比、占位形式和晶格畸变程度、自旋状态等进行表征,弥补传统红外光谱对于氮缺陷表征的不足。利用密度泛函理论(DFT)模拟不同氮缺陷的形成能解释实验观测的氮缺陷择优取向分布规律。根据对氮缺陷的聚集状态推算对应地幔存留时间和保存温度,追溯其形成过程和演变历史。     

湖南金刚石内部不均一性特征研究

将湖南金刚石加工成片，利用宝石显微镜，偏光镜，阴极发光（CL）仪和傅里叶红外光谱（FTIR）仪对其内部显微特征进行了研究，发现金刚石的颜色深浅不一，内外颜色差异明显，呈带状，斑状分布；金刚石由生长中心至边缘，氮含量也有较大变化，中心与边缘最大相差约50倍，氮的富集类型由中心向边缘表现出B中心所占的比例越来越小，金刚石的类型也相应从I型→II型或I－aAB型→-I-aA型等，这些不均一性特征，反映金刚石在生长过程中环境条件发生了变化，以及生长期后可能受到了改造。     

华北地台深部地幔流体的组成——来自金刚石不纯净组分的报道

从金刚石成因研究,流体包裹体、表征流体存在的固态包裹体及晶格原子、流体成分组合的制约因素等方面,论述了深部地幔流体的存在。华北地台原生金刚石中与流体包裹体共存的钛铁矿+铬铁矿、金红石+金云母+橄榄石、锆石+碳酸盐+橄榄石、磷灰石+金云母+橄榄石组合。相平衡原理揭示地幔流体存在着复杂的自催化反应。华北地台由金刚石流体包裹体所反映的深部地幔组成C、H、O、S和N分别为16.87%、47.47%、30.90%、3.02%和5.38%(皆为原子百分比),与现代大气圈、水圈相比明显富H贫O。     

国际拍卖市场彩色钻石价格（值）影响因素统计分析及其启示

近年来彩色钻石（简称彩钻）在国际拍卖市场上的重要性越来越明显,统计、梳理和定量分析近十年来苏富比、佳士得两大国际著名拍卖公司的彩钻拍卖记录,对研究彩钻价值的影响因素及其分级、价值评估具有十分重要的意义。研究结果显示,彩钻价格主要建立在颜色稀有程度及消费者偏爱之上,对价格影响最大的是其颜色色系、色彩瑰丽程度（饱和度、亮度和次要色调）;克拉单价通常与大小呈正比;净度、拍卖时间、来源（品牌）、类型等对其成交价格也有一定的影响。合成和经优化处理的彩钻可能会影响部分彩钻的价格,但总体上,其价格和天然彩钻价格之间没有发现必然联系。另外,高档彩钻在金融危机期间的表现显示其商品属性已从一般的奢侈消费品转变为资产投资品。上述结果说明,色彩、饱和度、亮度和次要色调是影响彩钻品质最重要的因素,就此而言,我国可参考美国GIA彩钻分级体系和澳大利亚力拓集团粉红色钻石的分级体系来建立适合中国市场的彩钻分级标准。     

巴西砂矿金刚石产地特征及比较研究

金刚石产地来源的确定是国际性难题,其中由于砂矿金刚石可能存在搬运过程的混合,其产地来源的确定更加具有争议性。巴西金刚石绝大部分来源于砂矿,从成矿地质背景、形貌和颜色、内部结构、矿物包裹体、微量元素、C同位素组成分布等六个要素总结分析了巴西金刚石研究的相关成果,为国际砂矿来源金刚石产地辨识提供参考。研究结果显示,巴西大部分矿区金刚石的特征与世界范围其它矿区的相似,以橄榄岩型为主,难以相互区分。但其中Juina地区和Machado河产地的金刚石具有独特的氮含量（无氮的Ⅱ型为主）和聚集状态,内部结构、矿物包裹体组合及温压环境特征均显示出深部地幔来源的特点,和巴西其它产地具有一定的区分度。与世界范围不同产地砂矿来源金刚石的基本特征对比显示,不同国家具体地区砂矿金刚石在上述不同要素的组合上存在一定的差异性,但总体上要借助现有资料进行产地来源的准确判断还非常困难,需要进行更深入细致的工作。     

Sites of the N1 nitrogen paramagnetic centers in natural diamond crystals: Dissymmetrization of the structure as a result of plastic deformation

Using the method of EPR spectroscopy, it is shown that the N1 nitrogen centers (N–C–N⁺) are unevenly distributed over possible sites in natural brown crystals of plastically deformed diamonds. The influence of deformational dissymmetrization of the structure on the anisotropy of some physical properties of natural diamonds is discussed.     

Zonal distribution of impurities in diamond

The zonal distribution of impurities in six diamonds (2 clear. 1 green-skinned, 2 green-bodied and 1 coated) was studied by neutron activation followed by dissolution of the diamond into a number of fractions. High surface concentrations of impurities found here and by other workers were attributed to both laboratory and natural contaminants. No unusual element distributions were found in the outer layer of the green-skinned diamond, the green skin probably being caused by natural radiation damage. The green-bodied diamonds had very different compositions from each other and from the other diamonds and it is suggested that such stones owe their colour to a high general level of impurities. All the diamonds, including the clear core of the coated diamond, contained impurities thought to be submicroscopic inclusions, either silicates, carbonates or immiscible sulphides derived from the parental magma. Variations in the composition of these inclusions in one diamond suggest changes in the host magma composition during growth. Sulphides apparently occurred in very small amounts throughout all the diamonds. Variations in the concentration of impurities are probably related to changes in growth rate or environment during diamond formation, and could explain some of the zonal variations in the physical properties of diamonds.     

湖南砂矿金刚石中杂质氮的存在形式和孤氮的分布特点

利用顺磁共振、紫外-可见吸收光谱和红外吸收光谱研究了湖南砂矿金刚石中杂质氮的存在形式和孤氮的分布特点。顺磁性氮的主要形式是孤氮心,氮的交换相互作用对和S=1的氮对心。非顺磁性氮的主要形式是双氮的和小片状氮的集合体。孤氮心分布的不均匀性不仅表现在晶体之间,而且体现在一个晶体的内部。氮的交换相互作用对和S=1的氮对心的出现与否和浓度大小的决定因素是晶体的孤氮浓度和孤氮在其中的分布特点。     

Luminescence spectroscopy and microscopy applied to study gem materials: a case study of C centre containing diamonds

The methods of luminescence spectroscopy and microscopy are widely used for the analysis of gem materials. This paper gives an overview of the most important applications of the analysis of laser and UV excited luminescence by spectroscopy and visually by microscopy with emphasis on diamond, and specifically natural type Ib diamond, little studied so far. Luminescence based techniques are paramount to the gemmological analysis of diamond, in order to determine whether it is natural, treated or synthetic. The great sensitivity of luminescence helps detect some emitting centres that are undetectable by any other analytical method. Hence, especially for diamond, luminescence is an enabling technology, as illustrated by its pioneering use of imagery for the separation of natural and synthetic diamond, and of spectroscopy for the detection of High Pressure–High Temperature treatment. For all other gemstones the applications are at the moment less numerous, but nevertheless they remain highly important. They provide quickly information on the identification of a gem material, and its treatment. Besides the study of broad band emissions caused by various colour centres, the typical PL-causing trace elements (amongst others) are chromium, manganese, uranium and rare earth elements. In pearls the study of broad band luminescence can be useful, and particularly the study of pink to red porphyrin luminescence in pearls from certain species such as Pinctada and Pteria and others can help identify the pearl-producing mollusc, or if a pearl has been dyed or not. Type Ib diamonds are representative of the importance and complexity of the analysis of luminescence by microscopy and spectroscopy. They show a wide range of sometimes very complex emissions that result in luminescence colours from green to yellow to orange or red. These emissions show generally very inhomogeneous distribution. They are caused by a range of defects, however only a few of them are well characterized.     

Structural defects in natural plastically deformed diamonds: Evidence from EPR spectroscopy

Structural defects formed as a result of plastic deformation in natural diamond crystals have been studied by EPR spectroscopy. The spectra of brown, pink-brown, black-brown, pink-purple, and gray plastically deformed diamonds of type Ia from deposits in Yakutia and the Urals were recorded. The results of EPR spectroscopy allowed us to identify various deformation centers in the structure of natural diamonds and to show that nitrogen centers were transformed under epigenetic mechanical loading. Abundant A centers, consisting of two isomorphic nitrogen atoms located in neighboring structural sites, were destroyed as a result of this process to form a series of N1, N4, W7, M2, and M3 nitrogen centers. Such centers are characterized by an anisotropic spatial distribution and a positive charge, related to the mechanism of their formation. In addition, N2 centers (probably, deformation-produced dislocations decorated by nitrogen) were formed in all plastically deformed diamonds and W10 and W35 centers (the models have not been finally ascertained) were formed in some of them. It has been established that diamonds with various types of deformation-induced color contain characteristic associations of these deformation centers. The diversity of associations of deformation centers indicates appreciable variations in conditions of disintegration of deep-seated rocks, transfer of diamonds to the Earth’s surface, and formation of kimberlitic deposits. Depending on the conditions of mechanical loading, the diamond crystals were plastically deformed by either dislocation gliding or mechanical twinning. Characteristic features of plastic deformation by dislocation gliding are the substantial prevalence of the N2 centers over other deformation centers and the occurrence of the high-spin W10 and W35 centers. The attributes of less frequent plastic deformation by mechanical twinning are unusual localization of the M2 centers and, in some cases, the N1 centers in microtwinned lamellae. Numerous data on models of deformation centers in natural diamonds, including the M2 and M3 centers, which were observed in the studied collection for the first time, are discussed.     

HPHT合成钻石在首饰中的鉴别特征

国家黄金钻石制品质量监督检验中心收到待检的百余件群镶钻石首饰中发现混有大量HPHT合成黄色钻石.采用宝石显微镜、红外光谱仪、X射线荧光光谱仪、紫外可见光分光光谱仪、紫外荧光灯、DiamondView^TM等对HPHT合成钻石样品做了详细地测试与分析.结果表明,这些HPHT合成钻石样品具有较为统一的黄色,放大检查可见合成钻石内部含有大量棒状、柱状、细小微粒状的铁镍合金包裹体,且几乎都有磁性,有些磁性甚至较强;样品的红外反射光谱非常特征,均具有明显的1 131 cm^-1处的吸收峰,为Ⅰb型钻石,而Ⅰb型钻石在天然钻石中极少见到;X射线荧光光谱测试显示有强烈的铁峰和镍峰,且在短波紫外线下多数具有绿黄色荧光.HPHT合成钻石在DiamondView^TM下具有不同程度的黄绿色荧光,部分具有黑十字现象.     

中国3个商业性钻石产地天然钻石的Diamond ViewTM图像及其意义

对采自我国3个商业性产地山东蒙阴、辽宁瓦房店、湖南常德地区的236片/颗天然钻石样品进行了系统的DiamondViewTM(DV)荧光图像分析,结合CL照相和FTIR的定量计算,探讨了钻石样品DV图像发光结构模式和荧光颜色方面的差异性及其原因。结果表明,3个产地钻石的DV图像和CL图像显示的钻石生长结构基本一致;钻石的发光结构模式与钻石内部氮、氢元素的种类和浓度分布趋势没有明显的一致性,DV图像模式并不完全受钻石类型控制,但DV图像的色调与钻石存在的杂质元素及晶体缺陷有关。钻石的DV图像特征受钻石的生长环境、结晶条件、后期熔蚀、辐照损伤等因素综合制约。从统计学的角度看,3个产地钻石的DV发光模式和荧光颜色有一定的差异,这种差异可以作为区分不同产地来源的钻石的宏观的统计学特征。DiamondViewTM技术在揭示天然钻石生长结构方面和CL发光照相技术效果近似,但更加便利。