六硝基茋的晶体结构及形貌模拟

培养得到六硝基茋(HNS)晶体,应用X-射线单晶衍射法测定了其晶体结构.结果表明,晶体属于单斜晶系P2(1)/c空间群,晶胞参数为a=2.198(2)nm,b=0.552 8(5)nm,c=1.466 3(13)nm,β=108.632(9)°,V=1.688 nm~3;Dc=1.771 g/cm~3;Z=4.将这些数据应用到Material Studio程序中的Morphology模块,计算模拟了六硝基茋3种可能存在的晶体形态,得到特定晶面的面积、附着能、表面能及晶面相对生长速率等参数.通过分析主要晶面的结构和相对生长速率对晶形的影响,得出选择官能团中含有活泼H原子和O原子的表面活性剂可更有效地控制六硝基茋晶体的形态.     

HMX晶体形貌的计算模拟

利用Material Studio中Morphology模块所含的BFDH、Growth Morphology和Equilibrium Morphology 3种方法计算了HMX的晶体形态和结晶习性;研究了重要晶面的结构、晶体的生长习性和晶面结构与晶形控制剂的关系.结果表明,Growth Morphology和Equilibrium Morphology方法的计算结果与实际比较吻合.     

金属氧化物纳米催化剂的晶面效应研究进展

纳米催化剂因尺寸效应具有优异的催化活性、选择性和稳定性,成为研究热点。在多相催化反应中,纳米催化剂不同的晶面因原子排布和密度不同,表现出不同的催化特性,即纳米催化剂的晶面效应。在纳米催化剂中,金属氧化物作为重要的催化剂和催化剂载体备受关注,通过对Ti O2、Co3O4和Ce O2金属氧化物特征晶面的表面结构进行分析,综述在特定催化反应中不同晶面催化性能和表面结构的关系以及不同晶面的表面结构在催化反应中的反应途径与机理。     

1,1′-二羟基-5,5′-联四唑二羟胺盐的晶形计算及控制

利用Materials Studio软件中Growth Morphology方法模拟计算了1,1′-二羟基-5,5′-联四唑二羟胺盐(TKX-50)的晶体形态和结晶习性,分析了主导晶面的表面结构特征;采用实验方法验证了模拟计算方法。结果表明,各稳定晶面在分子间距离、晶面电荷分布上存在很大区别。选择分子结构中具有负电子作用基团的晶体生长控制剂对其晶体形貌进行控制,可缩短快生长面和慢生长面之间生长速率的差距,减小晶体的形状系数。选择分子结构中含有富电子芳环的离子型表面活性剂为晶形控制剂,制备出了晶体形貌规整、呈多面体颗粒状、长径比明显变小的TKX-50晶体,试验结果验证了理论预测的正确性。     

2-硝亚胺基-5-硝基-六氢化-1,3,5-三嗪的晶体形貌预测

利用Materials studio 5.0软件包中的Morphology模块所含的BFDH、Growth Morphology和Equilibrium Morphology三种方法计算了2-硝亚胺基-5-硝基-六氢化-1,3,5-三嗪的晶体形貌,得到了特定的晶面的面积、表面能、附着能及晶面的相对生长速率参数,确定了形态学上重要的生长晶面。各晶面的结构分析表明,(011)和(021)为强极性晶面,(110)、(200)为极性晶面,(001)和(20-1)为弱极性晶面。据此可以预测,在强极性的质子溶剂中,(011)和(021)为形态学上的重要晶面,(110)、(200)、(001)和(20-1)晶面的显露可能增加。在非极性溶剂中,情况可能相反。     

CTAB对水热合成立方磷酸铋晶体及其界面结构的影响

采用水热法生长了立方磷酸铋晶体。研究了Bi与P摩尔比、合成温度、溶液p H值和表面活性剂十六烷基三甲基溴化铵(CTAB)浓度对软铋矿结构的立方磷酸铋晶体物相和晶面结构的影响。结果表明:Bi与P摩尔比为2:1和6:1,以及p H值为13和14时有利于立方磷酸铋的生成;CTAB的存在对晶体(100)面的生长有一定的抑制作用,同时会导致晶体出现(111)晶面。CTAB和温度同时变化时,(111)晶面由光滑晶面变为粗糙晶面。生长机制的变化是由于CTAB的存在导致阴离子生长基元的聚合以及CTAB与(111)晶面的相互作用。     

吡拉西坦在溶液环境下的晶习预测

根据吡拉西坦晶型Ⅱ和晶型Ⅲ的晶胞参数搭建晶体模型,对其进行空间优化和BFDH模型优化后,采用AE模型确定其晶面,对晶面上药物分子与溶剂分子可能存在的相互作用进行了探讨,通过分析各晶面的相对生长速率,确定其形态学上重要的生长面及其表面结构,预测吡拉西坦在溶液环境中的晶习。将模拟得到的吡拉西坦各晶型的晶体形貌与实际晶习比较,发现结果吻合良好。     

键合剂对HTPB与Al/Al2O3之间界面作用的分子模拟

采用分子动力学(MD)方法和COMPASS力场,研究了键合剂对丁羟推进剂中端羟基聚丁二烯(HTPB)与Al/Al2O3之间界面的吸附能与力学性能.结果表明,键合剂在Al2O3晶面的吸附能高于HTPB在Al2O3晶面的吸附能,而在Al晶面的规律并不明显.键合剂(TEA)与HTPB在Al2O3晶面吸附能远高于在Al晶面,Al2O3晶体(010)晶面高于 (001)晶面,Al晶体(001)晶面高于(011)晶面.两晶面中吸附能愈高,力学性能愈好.几种键合剂对吸附体系力学性能(弹性模量)的作用次序:TAZ＞TEA＞MAPO·HAC＞MAPO＞HX-752.     

FOX-7结晶形貌的分子动力学模拟

基于1,1-二氨基-2,2-二硝基乙烯(FOX-7)的晶胞参数,通过修正Dreiding力场得到了适用于FOX-7分子模拟的Dreiding-FOX-7力场;采用Growth Morphology方法模拟计算了FOX-7在真空中的晶体形貌,得到形态学上的重要晶面及附着能参数;构建了FOX-7重要晶面和H_2O/N,N-二甲基甲酰胺、环己酮的吸附模型;利用分子动力学方法计算出溶剂分子与各晶面的吸附能及各晶面的修正附着能;预测了FOX-7在溶剂中的结晶形貌,并与文献结果进行了对比。讨论了氢键的成键强度对晶体形貌的影响。结果表明,FOX-7在H2O/N,N-二甲基甲酰胺中(0 1 1)、(1 0-1)和(1 0 1)晶面为主要生长面,结晶形态为长方体块状;在环已酮中(0 1 1)和(1 0-1)晶面为主要生长面,结晶形态为长棱柱状,与文献结果一致。     

高指数表面晶面纳米γ-Al_2O_3的合成及表征

采用水热法合成了具有高指数表面晶面的扁六角片状纳米氧化铝,并用XRD、TEM、SAEDP、HRTEM以及N2吸附-脱附等技术对样品进行了表征,采用电子衍射和高分辨图像对其微观结构和显露晶面进行了研究。结果表明,合成的样品为具有高指数表面晶面的单晶扁六角片状纳米γ-Al2O3,侧表面显露晶面主要是{110}、{752}和{541}晶面族,上下表面主要显露{111}晶面族。纳米γ-Al2O3晶粒的尺寸主要集中在长度65 nm,宽度59 nm,厚度为5.5 nm,大小较为均匀,孔径分布较为集中。     

锗酸铋晶体缺陷和小面生长

对坩埚下降法生长锗酸铋闪烁晶体的缺陷进行了研究，除使用通常研究透明晶体的光学方法，由于ＢＧＯ晶体在受到光辐照损伤对短波长光具有高的吸收系数，因此还采用近紫外光吸收形貌法研究晶体缺陷，以及缺陷与晶体小面之间的关系，并根据ＢＧＯ晶体的结晶习性和小面形成机理提出了减少和消除晶小面生长及缺陷的方法。     

Tailoring crystal facet microenvironments for simultaneous electrochemical ozone and hydrogen peroxide production

Developing a bifunctional electrocatalyst that can effectively produce O₃ and H₂O₂ is significant for the electrochemical synthesis of O₃ and H₂O₂ for the synergistic oxidative degradation of organic pollutants. In this study, SnO with various exposed facets was synthesized by tailoring the crystal facet microenvironment for oxygen intermediates adsorption for electrochemical ozone production (EOP) and two-electron oxygen reduction reaction (2e⁻ ORR). The Faraday efficiency of SnO-1 with a high (110) facet ratio for O₃ was 22.0%, while SnO-4 with a high (002) facet ratio achieved a selectivity of 93.6% for H₂O₂. The theoretical calculation indicates that their excellent performances originated from the strong adsorption of the (110) facet on O* and O₂* and the suitable adsorption and desorption strength of the (002) facet on OOH*, respectively. This study provides an attractive strategy for the development of a bifunctional electrocatalyst for advanced electrochemical oxidation by tailoring the crystal facet microenvironment.     

尿素(520)晶面可控结晶的分子动力学模拟

由于尿素结晶呈白色针状,晶貌单一,且传统结晶工艺不可控,严重影响药物的一致性评价结果。采用分子动力学模拟方法,从分子水平上研究不同种类的添加剂对尿素晶体生长的调控作用,揭示添加剂对药物晶体生长的调控机制。结果表明：① 六种添加剂(海藻糖、蔗糖、葡萄糖、山梨醇、赖氨酸、精氨酸)在101.325 kPa、290 K下相较于无添加剂时都能不同程度地抑制(520)晶面的生长;② 添加剂对尿素晶面(520)的吸附能越负,其抑制晶面生长效果越好,其中海藻糖抑制(520)晶面生长效果最好;③ 添加剂分子携带基团的种类与数目决定与晶层的相互作用的强弱,特别是海藻糖、蔗糖双糖类分子含有8个羟基,与晶层上的尿素分子氢键相互作用强,与溶液层中的溶质形成竞争性吸附,能更好抑制(520)晶面生长。     

钒酸铋晶面调控制备及其降解四环素类抗生素性能研究

采用溶剂热法合成了单斜白钨矿型钒酸铋（m-BiVO₄）催化材料,采用XRD、BET、SEM、TEM等对其进行了表征。研究发现m-BiVO₄的形貌和晶面可以通过反应溶液的pH进行调控,在pH=7条件下制备出了具有（010）晶面择优暴露的m-BiVO₄（BVO-010）。以盐酸金霉素（CTC-HCl）、土霉素（OTC）、四环素（TC）和盐酸四环素（TCN）溶液为目标污染物,评价了制备材料的光催化降解性能。结果发现,与主要暴露热力学稳定的（-121）面的m-BiVO₄（BVO-121）相比,BVO-010的降解性能明显提高,光照150 min后对CTC-HCl、OTC、TC和TCN的降解率分别为77.9%、79.2%、63.6%和73.9%,可用于处理含抗生素类药物的污水。     

Screening of Oligopeptides that Recognize Inorganic Crystalline Facets of Metal Nanoparticles

Peptides that possess specific affinity to distinct crystal facets have been reported previously. However, their adsorption behavior in terms of the crystal sizes and shapes is less exploited. Herein, we isolate several phage clones that show the strong affinity to {100} of Pd at a neutral pH from the M13 phage library, and among them the phages that have shape selectivity to the cubic structure are identified by eliminating ones that bind randomly shaped Pd nanoparticles (NPs). Since Pd nanocube-binding phages are eluted by lowering pH values in the biopanning process, the selected phages (and their binding peptides displayed on protein pIII) can be released from Pd surfaces through pH changes. We used this feature to modulate the capping density of selected peptides on NPs. For example, when less peptides are capped on Pd nanocubes by lowering the pH values, the shape of the nanocubes is deformed and some evolve into a concave shape, indicating that Pd atoms are released from the less protected {100} facet selectively due to the higher surface energy. This type of crystalline facet-recognizing peptides can be applied for smart capping agents that not only bind target crystalline planes, but also modify their coverage on the specific surfaces with pH changes. The peptide-capping agents could be useful to fabricate NPs with characteristic shapes through etching and adsorption of atoms on specific crystalline planes of seed nanocrystals.     

Wetting Behavior of Ibuprofen Racemate Surfaces

The wetting behavior and detailed surface energetics of a racemate crystalline system were measured via contact angle measurements and inverse gas chromatography at finite concentrations. The advancing contact angles for water, diiodomethane, formamide, and ethylene glycol were measured on specific facets for racemic ibuprofen and S-(+)-ibuprofen single macroscopic crystals, and were found to be facet dependent for both systems. This observation demonstrates that variation in molecular orientation within the crystal lattice results in variations in exposed surface chemistry for differing facets, which results in anisotropic wetting behavior as previously reported. Surface free energy profiles of the ibuprofen racemates determined using a novel inverse gas chromatography method showed that powder samples (75–150 µm particle diameter) exhibited relatively homogeneous surface energies, with similar values of γ_SV ^d to those obtained by the contact angle analysis. These results lead us to conclude that ibuprofen exhibited a low level of surface heterogeneity, with the dominant facet of these powders exhibiting a low γ_SV ^d, with high energetic sites estimated to be < 3% of exposed available surface.     

Nucleation Barrier for Volume-Conserving Shape Changes of Faceted Crystals

This paper considers volume-conserving shape changes of small faceted particles or cavities; these changes are driven by surface-energy reduction. If these changes require normal motion of the facets (singular surfaces), and if the perimeter free energy σ_p (per unit area) of a nucleus of a new facet layer is comparable to a typical surface free energy (σ∼ 1 J/m²), the energy barrier is prohibitively large for facets larger than a limiting size of approximately a nanometer unless they are intersected by dislocations that provide a source of steps. In the absence of such dislocations, particles that contain these facets are immobilized in their initial shapes. If σ_p < σ, the limiting facet size is increased by a factor of approximately σ/σ_p.     

LiNbO_3纳米晶形貌模拟及其最佳纳米尺度计算

采用量子化学计算软件Material Studio的Morphology模块,运用BFDH法则对三方LiNbO3颗粒的纳米晶形貌进行了预测,并探讨了其纳米化的最佳尺度。模拟计算显示三方LiNbO3纳米晶的（112）、（112）面为最易外显面,显示几率为45.85%。通过对其纳米晶尺度的探讨,得出三方LiNbO3纯组分的最佳粒径为130nm。