Stacking fault formation in Ni?Zn f.c.c. alloys

X-ray diffraction study of the fault formation in Ni Zn alloys is carried out. Approximative analyses are performed in order to distinguish the influences of the dispersity and the microdeformations. Correlation between the X-ray diffraction data and the free molar Gibbs energy is looked for.     

Were J. Kepler and O. Krötenheerdt right?

It is established that one of the 12 Kepler nets (R, 3366 + 3636) belongs to Krötenheerdt nets. However, the number of Kepler nets remains 12, because one of them (L, 33336) is enantiomorphic. Along with 20 Krötenheerdt nets, there may be many other polytypes which enter infinite sequences of the O, OD, DO, D types.     

Cao.4Bao.6Nb2O6晶体的生长和低温拉曼光谱研究

采用提拉发生长了Ca0.4Ba06Nb2O6晶体,利用偏振拉曼光谱研究了Ca0.4Ba06Nb2O6晶体在低温25 ～260 K 范围内的结构稳定性.实验发现,随温度降低,NbO6六面体的内振动(v5)模的非对称性增加,由Gauss+ Lor Amp 拟合得出的相对低频(v5)模波数和相对高频(v5)模峰宽在70 ～100 K时发生突变,表明该晶体在此温度范围内可能存在相变.同时分别讨论了在x(口zz)x和x(zy)x不同偏振配置下,外振动模的相对强度比随温度的变化趋势,同样发现其在该温度范围内发生明显异常.最后简单讨论了布居因子对拉曼散射强度和实验结果的影响.     

Er3+:NaY(Wo.9Moo.1O4)2晶体的生长及光谱性能

采用提拉法(CZ法),生长出质量良好的Er3+:NaY(W0.9Mo0.1O4)2晶体.通过X射线粉末衍射,红外光谱分析,并与NaY(WO4)2相比较,得到Er3+:NaY(W0.9Mo0.1O4)2晶体的结构与NYW类似,仍为四方晶系的白钨矿结构,I4(1)/α空间群.测定了晶体的实际组成,得到晶体中各元素均按理论值进行掺杂,计算了掺杂离子的分凝系数约为1.15.在光谱性质上,测试了晶体的吸收光谱,及晶体在50～1000cm-1波数范围内的拉曼光谱,并计算了各吸收峰的半峰宽及吸收系数A.     

Quantitative UV–VIS spectroscopic studies of photo-thermo-refractive glasses. I. Intrinsic,bromine-related,and impurity-related UV absorption in photo-thermo-refractive glass matrices

The paper opens up a series of papers on the origin and parameters of spectral features forming the absorption of photo-thermo-refractive (PTR) glasses in the UV. Problems to be cleared for gaining further insight into the spectroscopic manifestations of species responsible for the photo-induced processes in PTR glasses are discussed. The samples of bromine-containing and bromine-free PTR glass matrices are synthesized and their absorption spectra in the 28,500 to 50,000 cm^–1 region are recorded. The dispersion analysis of the spectra is conducted based on the convolution model for the complex dielectric function of glasses. The matrix electronic transitions that set the real part of the complex dielectric function and form the intrinsic absorption tail of the matrix are simulated with a series of effective oscillators. Spectral features forming the total absorption spectrum of PTR glass matrices in the 28,500 to 50,000 cm^–1 region are deconvoluted. These features are (i) the intrinsic absorption tail, (ii) for the bromine-containing matrix, the low-wavenumber wing of an envelope around ~ 51,400 cm^–1 covering the bromine-related spectral feature(s), (iii) Fe²⁺- and Fe³⁺-related impurity bands, and also (iv) a structureless absorption mostly due to the high-wavenumber wings of other impurity bands below 28,500 cm^–1.     

Molecular complexes of sulfonamides. 3. Structure of 5-methoxysulfadiazine (form II) and its 1∶1 complex with acetylsalicylic acid

The X-ray structure of the biologically most active polymorph (Form II) of 5-methoxysulfadiazine (1) and that of the 11 complex between this sulfonamide and acetylsalicylic acid (2) are reported. The polymorph1 is monoclinic, space groupP2₁/c witha=13.086(2) Å,b=5.583(1) Å,c=17.222(3) Å, =99.98(1)°,Z=4 and occurs as centrosymmetric hydrogen bonded (N–H...N) dimers in the crystal. This arrangement differs from that observed in other polymorphs of the drug. Complex2 is triclinic, ,a=8.102(1)Å,b=12.033(1) Å,c=12.170(2) Å, =111.67(1)°, =93.77(1)°, =103.82(1)°,Z=2. Complexation involves linear intermolecular hydrogen bonds, N–H...O=C and N...O–H, between the amide group and pyrimidinyl N atom of the sulfonamide and the carboxylic group of the acetylsalicylic acid. On complexation to form2, neither molecular component undergoes any major structural change.     

Heterocyclic tautomerism. XI. Structures of 5,5′-bitetrazole and 1-methyl-5-(2′-pyridyl)tetrazole at 130 K

The X-ray crystal structures of 5,5-bitetrazole and 1-methyl-5-(2-pyridyl)tetrazole at 130 K are described. 5,5-Bitetrazole exists as the 1 H, 1'H-tautomer and packs in chains held together by pairs of intermolecular hydrogen bonds. It crystallizes in the monoclinic space group P2₁/n witha=4.945(1),b=6.367(1),c=8.491(1) Å and =99.233(7)^o. In 1-methyl-5-(2-pyridyl)tetrazole the two heterocyclic rings are nearly coplanar and the molecular packing is controlled by intermolecular – interactions. It crystallizes in the triclinic space group P1 witha=6.667(1),b=7.135(1),c=9.202(1)Å, =89.59(1), =69.08(1), and =66.62(1)^o.     

Complexation with diol host compounds. Part 2. Structures of 1,1,2,2-tetraphenylethane-1,2-diol and its 1∶2 molecular inclusion complex with dimethylsulphoxide

The structures of 1,1,2,2-tetraphenylethane-1,2-diol and its 12 molecular inclusion complex with dmso have been elucidated by X-ray crystallography from single crystal diffraction data. Crystals of the host, compound I, are monoclinic, space groupP2₁/n, witha=17.669(6) Å,b=6.144(6) Å,c=17.873(6) Å,=92.67(3)°,z=4. Crystals of the clathrate, compound II, are triclinic,P¯1, witha=9.138(5) Å,b=18.384(6) Å,c=18.496(3) Å,=61.16(2)°,=83.22(3)°, =88.06(3)°,Z=4. Both structures were solved by direct methods and refined to finalR values of 0.072 and 0.107, respectively. Compound I is partially disordered and its packing is governed by strong intermolecular hydrogen bonds. Compound II is characterized by crossing channels which accommodate the guest dmso molecules. The thermal properties of the latter compound have been characterized by DTA and TGA thermograms.     

Inclusion Compounds of Plant Growth Regulators in Cyclodextrins. Part VI. Study of the Inclusion Compound of MCPA in β-Cyclodextrin by X-Ray Crystallography

Abstract  

The structure of the 4-chloro-2-methylphenoxyacetic acid (MCPA) inclusion compound in β-Cyclodextrin (β-CD) has been investigated by X-ray crystallography. The inclusion complex crystallizes in the P2₁ space group with unit cell dimensions a = 15.860(2) ?, b = 24.275 (5) ?, c = 19.334(6) ? and β = 108.80(3)°. Its asymmetric unit contains two β-CD molecules which host two disordered MCPA guest molecules (2:2 host:guest stoichiometry) occupying overall five sites. It also contains 16.13 water molecules distributed over 36 sites. One water molecule is entrapped inside the dimeric cavity, forming a hydrogen bond with the chlorine atom of a guest. The two complexes of the asymmetric unit are located alongside and they form head-to-head dimers with the symmetry related complexes by the 2-fold screw axis (b-axis). The dimers form channels developed along the a-axis.