第35届中国化学奥林匹克初赛试题第4题的巧解*

对2021年第35届中国化学奥林匹克竞赛初赛试题中第4题进行了详细地解析。运用自己建立的模型,加深了学生对干冰晶体结构的认识,算出了与其相关的晶胞参数和原子坐标等,解释了干冰晶体为什么不是面心立方而是简单立方点阵。基于物质组成与结构的隐性关系,借助不饱和度巧妙地推出了各分子式可能具有的结构。同时对试题中存在的问题发表了自己的看法,并提出了一些教学建议。     

立方金刚石和六方金刚石结构的认识和应用

通过深入分析和对比立方金刚石和六方金刚石的结构,强化了对立方晶体和六方晶体的结构差别的认识,并以金刚石结构为基础建立了四面体型四配位晶体结构的模板以及衍生的四面体型四配位耦合直线型二配位的模板,利用模板分析具有类似结构的物质.     

第29至31届高中化学奥林匹克竞赛晶体结构试题解析

以第29-31届全国高中化学(奥林匹克)竞赛中晶体结构试题为例,从基础知识角度出发,对试题内容进行探讨,对命题思路及解题策略进行了分析,拓展了晶体结构类试题的研究背景和相关知识,引导读者了解试题背后的科学思想,感受化学学习的乐趣,并对今后化学奥赛中该类试题进行了展望,供参赛老师和学生参考。     

一硼化铪的晶体结构预测与构效关系基因

利用基于进化算法的晶体结构预测软件USPEX,并结合第一性原理方法对HfB的稳定晶体结构进行全局搜索。在基态条件下,新发现2个HfB晶体结构(空间群:P6m2和R3m)。其中,P6m2结构比已报道的Hf B晶体结构(空间群:Pnma、Cmcm、I41/amd和Fm3m)具有最低的基态能量。这些结构中,B原子分别以二维类石墨烯(P6m2和R3m结构),zig-zag链(Pnma、Cmcm和41/amd结构)和孤立原子(Fm3m结构)3种形式存在,从而导致它们具有显著的化学键合特征、高温稳定性和强韧特性差异。     

Materials Studio软件辅助中学化学教学*——以晶体结构为例

引入一种新的化学软件--Material Studio(MS),利用其晶体结构数据库和立体演示功能辅助晶体结构教学,并设计了典型化合物晶胞结构以及金属晶体晶胞堆积的演示实例和教学过程。MS软件的晶体结构演示功能简单易学,能帮助学生更好地掌握晶体结构知识点,实现个性化教学和学生自主学习,提高课堂教学效率。     

Waugh结构的H12[MnMo9O32(KO)6]的合成、晶体结构及催化性能

Waugh结构的H12[MnMo9O32(KO)6]的合成、晶体结构及催化性能;多金属氧酸盐;晶体结构;催化活性;Waugh结构     

Material Studio 7.0分子模拟软件在结构化学晶体结构教学中的应用

以3-氧杂双环（3.2.0）-1,4-庚二烯（OHD）晶体结构的构建为例,介绍了分子模拟软件Material Studio（MS）7.0在结构化学晶体结构章节中的教学应用,在三维晶体结构构建和优化的基础上,结合相关实验数据进行精修及定性定量物相分析,实现在微观结构层次对分子在三维空间的排列组合进行可视化展示,使学生能够直观、形象地理解有关晶体结构的抽象概念及理论。     

VESTA软件在典型晶体结构教学中的应用

晶体结构的基本概念既多又抽象,没有较强的空间想象力,很难理解和辨析清楚。二维图缺乏空间感;实物模型只做出一个晶胞,其重复规律不直观。VESTA晶体结构软件能够根据需要构建多个三维晶胞,即超胞,可以很直观地显示出晶体结构的特点。本文通过几个教学实例,说明VESTA软件如何帮助学生深入理解晶体结构的基本概念,结构特点与性能的关系,以及拓展晶体结构的认知领域,提高学习兴趣与探索能力。     

硼酸盐晶体及其溶液结构研究现状

硼酸盐结构十分复杂,主要针对硼酸盐晶体结构和硼酸盐水溶液结构问题,总结了水合硼酸盐晶体结构及其结晶行为,归纳了硼酸盐水溶液中硼酸盐的主要存在形式及其结构研究,并侧重介绍和评价了电导/电势滴定、红外(IR)、拉曼光谱(Raman)、11B核磁共振等方法在硼酸盐溶液结构研究方面的进展,指出了未来的发展方向.     

最密堆积中空隙分布的学习技巧

六方最密堆积和立方最密堆积是金属晶体中最常见的结构,其正四面体空隙和正八面体空隙的分布是学生学习的难点.本文将揭示密置双层-最密堆积-离子晶体结构中空隙的分布规律,进而将典型离子晶体结构与最密堆积中的空隙分布相关联.这对学生掌握空隙分布的规律性,理解金属和离子晶体结构,提升晶体结构的学习效果大有帮助.     

Estimation of Physico-chemical Properties of Ionic Liquid EPReO_4 Using Surface Tension and Density

An ionic liquid (IL) EPReO₄ (N‐ethylpyridinium rheniumate) was prepared. The density and surface tension values of the IL were determined in the temperature range of 293.15–343.15 K. The ionic volume and surface entropy of the IL were estimated by extrapolation, respectively. In terms of Glasser's theory, the standard molar entropy and lattice energy of the IL were estimated, respectively. Using Kabo's and Rebelo's methods, the molar enthalpy values of vaporization of the IL, Δ^g_lH⁰_m (298 K), at 298 K and, Δ^g_lH⁰_m (T_b), at hypothetical normal boiling point were estimated, respectively. According to the interstice model, the thermal expansion coefficient of IL EPReO₄ (α) was calculated and compared with experimental value, finding their magnitude order is in good agreement by 8.98%.     

离子液体BMIBF4性质的研究

用最大气泡法和韦氏天平法,在278．15～343．15K范围内测定了离子液体BMIBF4的表面张力和密度;讨论了这个离子液体的体积性质和表面性质;根据离子个头大又极不对称的特点,提出了离子液体的空隙模型．根据空隙模型计算的离子液体恒压热膨胀系数与实验值相比,偏差在10％左右。     

Studies on the properties of ionic liquid BMIInCl4

An ionic liquid (IL) was prepared by directly mixing InCl₃ and 1-methyl-3-butylimidazolium chloride(BMIC) with molar ratio 1:1 under dry argon atmosphere. The densities, and surface tension of pure IL were determined at temperature range of (278.15 to 343.15±0.1K). The properties for ionic liquid based on group III were discussed using Glasser’s theory. The standard entropy, the surface energy and the crystal energy of ionic liquid were calculated, respectively. The crystal energy of ionic liquid is much lower than ionic solid and this is the underlying reason for forming ionic liquid at room temperature. In addition, a new theoretical model of IL, that is interstice model, was applied to calculate the thermal expansion coefficient of BMIInCl₄. The order of magnitude for the thermal expansion coefficient, a, calculated by the theoretical model is in good agreement with experimental value. The result shows that there is much reasonableness for the interstice model of ionic liquid. __________ Translated from Chemical Journal of Chinese University, 2005, 26(10)(in Chinese)     

Phase transition of Fe(dpm)<Subscript>3</Subscript> in the range 243–210 K

The volatile Fe(dpm)₃ complex was studied by X-ray diffraction at 243 K and 210 K. A phase transition from monoclinic to triclinic structure was found in the temperature range 236–226 K. The packing of complexes in the structures is analyzed by the procedure of translation sublattice isolation. The motif of mutual arrangement of Fe atoms is pseudohexagonal in both modifications. Apart from the differences in the Fe...Fe distances, there are differences in rotation of definite chelate rings.     

离子液体BMIBF4性质的研究

用最大气泡法和韦氏天平法, 在278.15～343.15 K范围内测定了离子液体BMIBF₄的表面张力和密度; 讨论了这个离子液体的体积性质和表面性质; 根据离子个头大又极不对称的特点, 提出了离子液体的空隙模型. 根据空隙模型计算的离子液体恒压热膨胀系数与实验值相比, 偏差在10%左右.     

Impact of co-doping concentration in copolymer network liquid crystals

ABSTRACT

The impact of varying the co-doping concentration of a mesogenic and a non-mesogenic monomer in the reactive mixtures used to create a copolymer network LCs was investigated. Use of copolymer has been found to improve the response properties in the obtained liquid crystal composites. The polymer network in the studied copolymer network LCs was examined by scanning electron microscopy and the response times in various samples were investigated. Samples were prepared with various reactive mixtures, each of which had a constant concentration of mesogenic monomer, various concentrations of non-mesogenic monomer, and the same amount of photoinitiator. These reactive mixtures were filled in home assembled test cells with planar alignment and then exposed to UV light. With increasing concentration of the non-mesogenic monomer, the response properties of the resulting copolymer network LC were improved. Usually, if the overall polymer content in a polymer network LC is increased, the threshold voltage is also increased. However, both threshold voltages and response times were lowered and the response properties were thus improved in the studied copolymer network LCs. This unexpected behavior could be traced back to inducing a grainy polymer morphology of the copolymer network by using a non-mesogenic monomer.     

Applications of multidirectional reflective light-control films on reflective polymer-dispersed liquid crystal displays for enhancement in image quality at lower viewing angles

In this paper, multidirectional light-control reflective (LCR) films are developed in order to create an active reflective structure that will enhance the image brightness and contrast ratio of reflective dye-doped polymer-dispersed liquid crystal (D-PDLC) displays at lower viewing angles. Advantages of LCR films are that their production is low cost and they require a simple photolithographic fabrication method. The optimum design prism-type light-control reflective film succeeded in minimising the surface scattering effect; thus, the contrast ratio is much enhanced. The symmetric and asymmetric LCR films produced multidirectional scattering that enhances the reflectance at lower viewing angles, which has importance in future display applications. In particular, the prism LCR film has been found to be more influential on the reflectance of D-PDLC films due to multidirectional scattering of light by non-symmetric arrays. The improvement in contrast ratio has been confirmed by the enhancement of optical properties for reflective D-PDLC displays at lower viewing angles below 30°.     

Crystalline Behavior and Structure of a Liquid Crystal Compound, 5‐{[4′‐(((Pentyl)oxy)‐4‐biphenylyl)carbonyl]oxy}‐1‐pentyne

Single crystals of two liquid crystal compounds, 5‐{[4′‐(((pentyl)oxy)‐4‐biphenylyl)carbonyl]oxy}‐1‐pentyne (A3EO5) and 5‐{[(4′‐nonyloxy‐4‐biphenylyl)carbonyl]oxy}‐1‐pentyne (A3EO9), have been prepared by solution growth technique. The morphologies and structures of A3EO5 and A3EO9 crystals were investigated by wide angle X‐ray diffraction (WXRD), atom force microscope (AFM) and transmission electron microscope (TEM). In contrast to the same series of compounds which have a longer alkyl tail, 5‐{[(4′‐heptoxy‐4‐biphenylyl)carbonyl]oxy}‐1‐pentyne (A3EO7), 5‐{[(4′‐heptoxy‐4‐biphenylyl)oxy]carbonyl}‐1‐pentyne (A3E′O7) and A3EO9, A3EO5 shows strikingly different crystalline behavior. The former three compounds have only one crystal form, whereas A3EO5 exhibits polymorphism. Specifically, A3EO5 crystals grown from toluene solution show two crystal forms. The first one is crystal I which adopts a monoclinic P112/m space group with unit cell parameters of a?5.79 Å, b?8.34 Å, c?43.92 Å, γ?96°, and the other one is crystal II which adopts a monoclinic P112 space group with unit cell parameters of a?5.55 Å, b?7.38 Å, c?31.75 Å, γ?94°. When using dioxane as the solvent to grow A3EO5 crystal, we can selectively obtain crystal I. A3EO5 melt‐grown crystals also have two crystal forms which derive from crystal I and crystal II, respectively. The different crystalline behavior of the compounds should correlate with their different electron dipole moment resulting from the different length of alkyl tail.     

谈谈聚合物的结晶形态问题

向读者引介了聚合物球晶的三维立体电镜照片，并介绍了高分子科学近年来的新研究成果－尺寸已达厘米量级的聚合物宏观单晶体和只由一根大分子链结晶而成的高分子单链单晶的特殊形态。     

反蛋白石光子晶体的研究进展

反蛋白石晶体是一类重要的光子晶体,由于其制备材料的广泛性以及容易实现对光子禁带的多重调制而受到广泛关注.本文介绍了目前反蛋白石晶体结构的主要制备技术和方法,详细阐述了反蛋白石晶体结构的最新研究进展.