准晶三阶非线性弹性的轴转动对称性

用群论方法导出具有轴转动群SO(2)对称性的三阶非线性弹性系数张量的一般形式.指出具有十次对称轴的准晶的声子型三阶非线性弹性系数张量具有围绕十次对称轴的任意旋转对称性.     

二阶非线性弹光张量的旋转不变性

基于群论原理,用Matlab语言编制了用于计算具有SO(2)群对称性的任意阶弹光系数张量的通用软件.在编程中,采用由非对称化的恒等表示基函数构造出具有弹光系数张量本征对称性的对称化恒等表示基函数的方法,以便于编制通用软件.利用该软件得到了具有SO(2)群对称性的二阶非线性应变和应力弹光系数张量的形式,并经坐标变换验证,该张量形式确实具有围绕物理坐标系中Z轴的任意旋转不变性.     

晶体物理性质的空间轴转动对称性

用群论方法导出具有SO(2)群对称性的一般三阶、四阶张量形式;进而给出具有这种对称性的压电、线性电光、二阶非线性极化、弹光、二次电光、电致伸缩、弹性及三阶非线性极化系数矩阵的一般形式.指出含有4度或6度转轴的非中心对称晶类的压电、线性电光及二阶非线性极化性质,以及所有六方晶类的弹光、二次电光、电致伸缩、弹性及三阶非线性极化性质具有关于晶体中唯一高次轴的任意旋转对称性.对所得结果作了讨论.     

高阶电光和电致伸缩张量的旋转不变性

根据群论原理,用Matlab语言编制了用于计算具有SO(2)群对称性的任意阶电光和电致伸缩系数张量的通用软件.利用该软件得到了具有SO(2)群对称性的三次和四次电光系数张量以及二阶和三阶电致伸缩系数张量的一般形式,并经坐标变换验证,这些张量形式确实具有围绕物理坐标系中z轴的任意旋转不变性.     

La3Ga5SiO14的BAW传播特性

详细推导计算了声体波(BAW)在La3Ga5SiO14(LGS)晶体中分别沿YZ、XY、XZ面传播的纯切变波,准切变波,准纵波的表达式.绘制了LGS晶体在(100)、(010)、(001)这三个主晶面内声的慢度分布曲线图.计算了声速的最大值并与石英进行比较,结果表明LGS晶体的BAW传播速度一般比石英低1000m/s左右.为该晶体在声体波器件等方面的设计和应用提供了一定的理论指导作用.     

K2SO4晶体枝状形貌及结晶学模型

生长了具有枝状形貌的K2SO4晶体.基于单偏光显微镜下的形貌观察和背散射电子衍射分析,测定了枝晶的生长方向,建立了K2SO4晶体枝状形貌的结晶学模型.研究表明,K2SO4晶体的生长方向为[111]方向和[(1)-(1)1]方向,且两者夹角为114.4°;发育的晶面为(1(1)0)面,是由[111]晶向和[(1)-(1)-1]晶向组成的晶面.K2SO4枝晶具有两种生长模型,当其作为单枝生长时,一个< 111>方向的枝体连续发育做主枝,另一个<111>方向的枝体不连续发育作为侧枝;当其多枝同时生长时,<111>方向既可作为一个主枝,又可以作为其它主枝的一个侧枝.两种模型均指示出了K2SO4枝晶生长的不对称性.该研究揭示了结晶学方向在枝晶形成过程中的控制作用.     

CaO-MgO-Al2O3-SiO2-P2O5-(F)微晶玻璃的析晶及特征

采用熔融法制备了不同P2O5及F含量的CaO-MgO-Al2O3-SiO2-P2O5-(F)基础玻璃试样,研究了CaO-MgO- Al2O3-SiO2-P2O5-(F)系微晶玻璃的析晶及特征.结果表明:在CaO-MgO-Al2O3-SiO2-8.0wt;P2O5玻璃中,表面析晶和内部析晶同时存在,析出晶体主要为钙长石(CaAl2Si2O8)相、硅灰石(CaSiO3)和α-磷酸钙(Ca3(PO4)2).玻璃中P2O5含量的提高抑制玻璃的表面析晶,同时促进了玻璃的整体析晶和α-磷酸钙晶体析出.同时添加P2O5和F的玻璃试样以整体析晶为主,析出晶体为块状氟磷灰石和粒状钙长石相.     

MMTN晶体与MMTWD晶体的晶格振动及热导率的拉曼光谱研究

采用拉曼光谱技术测量了MMTN(MnHg(SCN)4(C2H5NO)2)和MMTWD(MnHg (SCN)4(H2O)2(C3H7NO)2)两类金属有机配合物晶体的拉曼光谱,并对其晶格振动特征峰进行了指认.依据晶格动力学理论以及声子散射模型,推导了晶体热导率与声子寿命及拉曼谱线半峰宽的关系,计算了晶体的热导率,讨论了该类晶体激光损伤的物理机制.     

Cs4SrI6:Eu晶体的生长和闪烁性能研究

采用垂直布里奇曼法成功生长了一种Cs4SrI6:3;Eu闪烁晶体.毛坯晶体尺寸最大为φ25×70 mm3,是目前最大的Cs4SrI6:Eu单晶.XRD结果表明,晶体具有K4-CdCl6晶体结构,属于R-3C空间群,通过紫外-可见荧光光谱和X射线激发发射光谱,研究了晶体的荧光性能.研究了在137Cs662 keV辐射下Cs4SrI6:Eu单晶的闪烁性能和衰减时间,表明该晶体具有较高的光输出和优良的能量分辨率,衰减时间约为1.86μs.通过分析Eu2+在晶体中不同部位的浓度,计算出Cs4SrI6:Eu晶体中Eu2+的分凝系数约为1.136,结果表明Cs4SrI6:Eu晶体在辐射探测中具有潜在的应用前景.     

沿[001]c方向极化PZN-xPT单晶的声表面波性能

利用半波解法对三方相、四方相及准同型相界附近,沿[001]c方向极化(1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3晶体的声表面波传播特性进行了对比研究.结果表明,位于准同型相界附近的0.92Pb(Zn1/3 Nb2/3)O3-0.08PbTiO3晶体的声表面波性能明显优于三方相0.955Pb(Zn1/3Nb2/3)O3-0.045PbTiO3和四方相0.88Pb(Zn1/3Nb2/3)O3-0.12PbTiO3晶体.具有复杂工程畴结构的0.92Pb(Zn1/3Nb2/3)O3-0.08PbTiO3晶体声表面波机电耦合系数显著高于四方相晶体.同时0.92Pb(Zn1/3 Nb2/3)O3-0.08PbTiO3晶体具有相对较小的声表面波相速度和能流角.因此,该晶体适合制作机电性能优越的声表面波器件.     

Orientational Order of Spin Probe Molecules in Liquid Crystals

We report here measurements of hyperfine splittings and g values of two nitroxide spin probes 4',4'-dimethyl-spiro-(5α-cholestane-3,2'-oxazolidin)-3'-yloxyl and 2-(10-carboxydecyl)-2-hexyl-4,4-dimethyl-3-oxazolidinyloxyl methyl ester dissolved in p-azoxyanisole. Using the principal axes values of g and A tensors available, we have determined all three diagonal components of the orientational order parameter tensor S for these spin probe molecules. We find that for neither of the spin probes used here has this tensor S the cylindrical symmetry that is normally assumed to determine the orientational order parameter tensor S^(p) defined by the long molecular axis from such measurements. We show further that this conclusion about S is independent of any uncertainty in the principal axes values of the g and A tensors, and hence the relations between S and S^(p) normally used do not seem to be well justified. Probable relations are also suggested.     

Modern application packages for rigorous solution of problems of light propagation in anisotropic layered media: II. Optically active crystals

The matrix Δ suggested by Berreman for optically active crystals of various symmetry classes has been calculated with the use of the Mathematica-4.1 package. It is shown that the eigenvalues of this matrix are the refractive indices, whereas its eigenvectors determine the polarization states of eigenwaves propagating in the crystal. The relation between the components of the gyration tensors obtained on the basis of various constitutive equations is established. The essential differences in the optical activity described on the basis of these equations are also discussed.     

Electrostatic model of the α-LiIO<Subscript>3</Subscript> pyroelectric

The range of possible combinations of the components of the electronic-polarizability tensors of oxygen and iodine ions and the effective charges of these ions is established on the basis of the experimental study of the parameters of the electric-field gradient tensor at ⁷Li nuclei in an α-LiIO₃ crystal and the calculation of the electric-field gradient from the classical electrostatic model. The I-O bonds in α-LiIO₃ are shown to be mixed ionic-covalent bonds with low ionicity. Spontaneous polarization of the crystal is estimated.     

Improper ferromagnetic phase transitions in crystals

A complete set of possible improper phase transitions leading to polarization and magnetization of crystals is found from tensor bases of representations of the black-and-white point group of crystal symmetry by using the multiplication table of irreducible representations. The dependences of the secondary order parameter on the primary order parameter are presented for different classes of the symmetry group.     

Experimental Solution of the Local Field Problem in Uniaxial Liquid Crystals†

A method of experimental determination of the Lorentz-factor tensor in uniaxial liquid crystals is suggested. The specific features of the local field tensor of the light wave in a nematic liquid crystal with low optical anisotropy have been investigated experimentally. Anisotropy of the local field and Lorentz-factor tensors has been found to decrease with the decreasing optical and molecular-optical anisotropies. These results appear to contradict the existing polarization theories of liquid crystals. The local field problem in cholesteric liquid crystals has been considered. A new approach to the local field problem in uniaxial liquid crystals with arbitrary optical anisotropy is developed and the experimental results are explained.     

Growth of functional single crystals of complex compounds on the basis of the solubility phase diagrams of ternary systems

The validity of solubility phase diagrams of ternary systems for determining the optimal (concentration and temperature) dynamic growth conditions for single crystals of congruently and incongruently dissolving solid phases is shown. It is found that the optimal composition of the mother liquor for growing solid-phase single crystals corresponds to the solution in the solid-phase solubility curve that is located at the maximum distance from the points of invariant equilibria. More than 40 ternary systems have been used and more than 60 new and known large functional single crystals of stoichiometric composition and optical quality that belong to different chemical classes have been grown on their basis under dynamic conditions.     

CNDO/2-FPP Polarizabilities

Polarization functions have been added to the CNDO/2 basis set to reproduce a minimal set of experimental polarizability tensors for 13 model molecules containing H, C, N, O, F, P, S, Cl, Se, and Br without affecting occupied molecular orbital energies or atom-in-molecule charges. The resulting CNDO/2-FPP program yields excellent molecular and atom-in-molecule polarizability tensors for almost any molecule containing these elements.     

3-叔丁基-1-(3-羟基苯基)脲的晶体结构及密度泛函理论研究

脲类及其衍生物在化学、农业、医学等多个领域有重要用途。而芳基脲类化合物是一类重要的医药化工中间体,本文经酰化和氧化两步反应制备3-叔丁基-1-(3-羟基苯基)脲,并于室温下经溶剂挥发法获得其单晶体,对晶体的堆积及分子间作用模式进行了分析。其结构经核磁共振氢谱(¹H NMR)、红外光谱(FT-IR)、核磁共振碳谱(¹³C NMR)、质谱MS和X射线单晶衍射等方法确证,在B3LYP/6-311+G(2d, p)模式下使用密度泛函理论(DFT)进行了最优结构以及前沿轨道能量计算,对比了晶体与理论计算的分子结构。结果表明,经DFT优化的分子结构与X-射线单晶衍射确定的晶体结构基本一致,该化合物为单斜方P2₁/n空间群,晶胞参数为a=1.181 42(6) nm,b=1.762 00(8) nm,c=1.179 02(5) nm,Z=8。