共查询到17条相似文献,搜索用时 849 毫秒
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m-NBA*DEA和3.5-DNBA*DEA分子晶体形貌的分析 总被引:1,自引:0,他引:1
本文应用周期键链理论(Periodic Bond Chain;简称PBC),结合晶体的结构数据,采用文献[1]给出的计算接触能(Eatt)的公式,通过微机对间硝基苯甲酸(m-NBA)和3.5-二硝基苯甲酸(3.5-DNBA)分别与二乙醇胺(DEA)形成超分子化合物(分别简称为m-NBA*DEA和3.5-DNBA*DEA)的晶体形貌及生长习性进行了推断.其结果是:m-NBA*DEA晶体属于F面的单形有{001};属于S面的单形有{011},{101},{110},{100}和{112};其它单形则属地K面.对于3.5-DNBA*DEA晶体,由于在晶体结构中只有一个PBC矢量,故不出现属于F面的单形;而属于S面的单形有{010},{001}和{011};其它单形则属于K面.实验证明,理论推算的形貌与实际晶体的形貌符合得比较好. 相似文献
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配合物晶体MnHg(SCN)4中维系晶体结构的化学键是-Mn-NCS-配位键.从MnHg(SCN)4晶体中配位键的分布特点出发,对属于点群4的单形四方四面体、四方柱和平行双面进行分析,确定晶形中不能出现平行双面{001}、四方柱{110},可以出现的单形为四方四面体{101}和{011}及四方柱{100},而且四方四面体{101}和{011}单形最发育.由结构分析得出的晶形特点与实际晶体晶形特点相符. 相似文献
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晶体中正负离子半径比(R+/R-)与晶胞和结晶形态 总被引:1,自引:0,他引:1
本文研究了AB型晶体中正负离子半径比(R+/R-)与晶胞和单形的显露以及硅酸盐系列晶体中的络阴离子结晶方位和对称分布与晶体的形貌的密切相关性,从中找出与结晶形态的相关性.提出晶胞界线是以负离子配位多面体的面、棱和角为界面而划分的;晶体中负离子配位多面体的对称性与晶体形态的对称性是对应一致的.由此进一步阐明了组成晶体结晶形态的结构基元是负离子配位多面体. 相似文献
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紫外非线性光学晶体三硼酸铯的生长和性能 总被引:3,自引:3,他引:0
采用泡生法和提拉法生长出三硼酸铯(化学式CsB3O5,简称CBO)晶体,研究了晶体生长工艺条件及晶体生长形态.泡生法生长的CBO晶体的尺寸为40mm×25mm×25mm;生长过程中晶体转速为10~20r/min,降温速率为0.1~0.2℃/d.用提拉法生长出20mm×30mm的CBO晶体;生长过程中液面温度梯度为60℃/cm,提拉速度为8mm/d.在生长过程中Cs2O的挥发速度大于B2O3的挥发速度.CBO单晶的晶面由[011]斜方柱和[010]斜方柱单形组成,属于[011]单形是4个较大的面,属于[101]单形是4个较小的三角形晶面.CBO在紫外波段具有较大的有效非线性光学系数.利用CBO进行Nd∶YAG激光和频获得了高转换率的波长355nm及266nm相干光输出. 相似文献
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化学计量比LiNbO3晶体的畴结构及完整性研究 总被引:2,自引:2,他引:0
本文对用助熔剂提拉法生长的两种化学计量比LiNbO3晶体进行了测试分析,并与同成分LiNbO3晶体相比较.通过差热分析和X射线粉末衍射测试,得出随着晶体中Li2O含量的增加,其居里温度变高,晶格常数变小.用酸腐蚀晶体,通过直接观察和金相照片,分析其畴结构,得出SLN11是单畴生长,首次观察出SLN19晶体在Z切面上出现了三块面积较大的对称反畴区,将其称为区域性单畴.另外,还对晶体在(001)方向抛光面的不同位置测量了其回摆曲线,得到了其中SLN19晶体有着较完整的结晶面.期望通过改变生长参数,长出完全单畴且更加接近化学计量比的LiNbO3晶体. 相似文献
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ZnGeP2单晶生长与安瓿设计研究 总被引:1,自引:1,他引:0
根据晶体自发成核几何淘汰规律,结合ZnGeP2晶体的结晶习性,研究设计出生长完整ZnGeP2单晶体的双层镀碳石英安瓿,其关键技术参数为:安瓿长径比6~7,籽晶袋长度≥25 mm,安瓿主体与籽晶袋之间的放肩角在25°左右.在上述生长安瓿中,采用改进的垂直布里奇曼法,分段控制下降速率,成功生长出尺寸为22 mm×40 mm的ZnGeP2单晶.对晶体进行X射线分析,获得(204)面单晶衍射谱和回摆谱,衍射峰峰形尖锐无劈裂,回摆谱对称性好,半峰宽为0.063 °;晶片在2~12 μm波段范围内的红外透过率达50;以上.实验结果表明,研究设计的生长安瓿适合于磷锗锌单晶生长,能够获得较高质量的单晶体. 相似文献
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本文采用NaOH-KOH混合熔融物和KOH溶液对石榴子石晶体各种不同的结晶学方向的晶面(切面)进行腐蚀实验,建立了石榴子石碱腐蚀像的立体模型,并与酸(HF溶液)腐蚀像模型进行对比.研究发现碱腐蚀像与酸腐蚀像一样能很好的反映晶体的对称特点,并发现在{ 100}、{110}晶面(切面)上碱腐蚀像与酸腐蚀像相同,而在{120}、{221}、{111}、{211}晶面(切面)上,碱腐蚀像与酸腐蚀像不同.该研究可以用来对石榴子石族矿物进行结晶学定向,同时具有揭示矿物所处地质环境酸碱性的指示意义. 相似文献
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Gallium orthophosphate (GaPO4) single crystals were grown by the reverse temperature gradient method from phosphoric acid solutions under hydrothermal conditions. Twins after (110) were studied by etching faces having been cut perpendicular to one of the twofold axes. Based on the determination of the twin boundary position as well as on the knowledge of the growth rates of different crystallographic forms, a few faces have been chosen to be quite promising for growing high‐quality GaPO4 single crystals if they are offered at the referring seed crystal. From the characterization of the grown crystals conditions have been found, which may lead to the reduction of the inversion twin number during the growth process. 相似文献
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The investigation on the mechanism of nucleation and growth of crystals at organic‐inorganic interfaces is crucial for understanding biological and physiological calcification processes such as the formation of urinary stones. The effects of five different amino acids on the crystallization of calcium oxalate have been investigated at pH 4.5 and 37 °C in aqueous solutions in the batch type crystallizer. The products were characterized by Scanning Electron Microscopy (SEM), Fourier Transfer Infrared Spectroscopy (FT/IR) and X‐Ray diffraction (XRD) analysis. Crystal size distribution (CSD) and filtration rate measurements were done. In order to determine the adsorption characteristics of amino acids on the calcium oxalate crystal surfaces, zeta potential measurements were also done and discussed. The results indicate that in the presence of all investigated amino acids, calcium oxalate monohydrate (COM) crystals were preferentially produced, but the crystal morphology varied with amino acid types and concentrations. Various crystal morphologies such as elongated hexagonal, coffin or platy habits were observed. In the presence of all investigated amino acids, the calcium oxalate crystallized in a monohydrate form. Electrostatic/ionic interaction, different adsorption properties and special functional effects of amino acids led to find different crystal morphology. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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The twinning morphology of β-BaB2O4 crystal grown by TSSG has been studied on the basis of crystallography. It was found that the faces R{101-2} and r{011-4} are often intergrown together by either r{011-4} intergrown in R{101-2} or in reverse, two individuals mostly take X(112-0) and occasionally take Y(011-0) as twin boundary; and that two individuals in the twin could take the same or opposite crystallographic polarity, this was identified by surface etched figures and the piezoelectric measurements. The formation of the twinned crystals are discussed from the crystallographic structural characteristics and the energetic considerations. The experimental factors such as crystal seed quality are suggested to reduce or eliminate the twin formation and to improve the crystal quality. 相似文献
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The morphological features of ZnO crystallites influenced by solution basicity under hydrothermal conditions have been studied from the standpoint of the incorporation of the growth units. A crystal chemistry approach is developed to understand and thus to control a desirable morphology of the crystallites. The effects of the additive OH− on the crystal morphology of ZnO crystallites are qualitatively but satisfactorily explained by a mechanism considering two aspects: (1) solution structures and the structural forms of growth units under a certain growth condition, i.e. the interactions between the solvent molecules and the growth units; and (2) the influence of the solvent molecules or additives on growth interfaces, particularly on two polar faces of ZnO crystallites in terms of the inhibition or promotion of the incorporation of various growth units depending on the solution basicity. Since the incorporation rates of the growth units are different on positive and negative polar faces, the relative growth rates of these faces are different and thus lead to the habit modifications. The approach clearly demonstrates that the hindrance of crystal growth is a consequence of surface adsorption processes. 相似文献
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Simple crystal forms are analyzed as the orbits of point symmetry groups on a set of crystal planes of space. All known polyhedra are described and structurized based on the theory of the orbits of groups, which provided a new, more harmonious approach to this problem. The orbits of groups can be general or particular and characteristic or non-characteristic. All possible versions of all crystallographic groups are listed in the table. The problem of the equivalence of polyhedra as the orbits of point symmetry groups is considered. An analysis of this problem has shown that 32 point crystallographic symmetry groups correspond to 139 symmetrically nonequivalent polyhedra. 相似文献