ZrSiO4∶Ti3+晶体的电子顺磁共振参量理论研究

基于离子簇模型,采用d1在四角伸长四面体对称中电子顺磁共振(EPR)参量的高阶微扰公式,计算了ZrSiO4 晶体中处于Si4+位的四角Ti3+中心的EPR参量(g因子g//,g⊥和超精细结构常数A因子A//,A⊥).由于配体O2-与中心金属离子Ti3+的旋轨耦合系数大小相近,在这些公式中同时考虑了配体p、s轨道及旋轨耦合作用对EPR参量的贡献.公式里的能级分裂由叠模型和杂质中心的局部结构确定.研究发现,掺杂后形成的四面体团簇[TiO4]5-相对母体产生了约0.3°的角度畸变.计算所得的EPR理论值与实验值符合的很好.     

SrCl2∶Ag2+晶体局部结构及电子顺磁共振参量的理论研究

基于离子簇模型,采用d9离子在四角伸长八面体对称中电子顺磁共振(EPR)参量的高阶微扰公式,计算了SrCl2中四角Ag2+中心的EPR参量(g因子g//,g⊥和超精细结构常数A因子A//,A⊥).由于体系的共价性及配体Cl-较大的旋轨耦合系数,在这些公式中同时考虑了配体轨道及旋轨耦合作用对EPR参量的贡献.公式里的能级分裂由重叠模型和杂质中心的局部结构确定.研究发现,掺杂后由于尺寸失配,杂质Ag2+沿着C4轴有一个很大的非中心位移,到最近邻的Cl-平面距离约为0.060 nm.计算所得的EPR理论值与与实验值符合的很好.     

晶体zinc 1-malate trihydrate∶Cu~(2+)的自旋哈密顿参量及局部结构的理论研究

在晶体场理论的基础上,利用四角对称3d9离子自旋哈密顿参量高阶微扰公式计算了Zinc 1-malate trihydrate:Cu2+的g因子(g//,g⊥)和超精细结构常数(A//,A⊥)。结果表明,由于Jahn-Teller效应,Zinc 1-malate trihydrate:Cu2+晶体中配体氧八面体沿C4轴方向伸长约0.0033 nm,络离子[CuO6]10-的键长R//≈0.2157 nm,R⊥≈0.2058 nm;局域结构沿C4轴方向呈伸长八面体结构。所得EPR参量理论计算与实验符合较好,并对上述结果进行了讨论。     

Cu2+在晶体K2Cd(SO4)2·6H2O中的电子顺磁共振参量及局部结构的理论研究

在晶体场理论的基础上,由重叠模型建立了杂质中心结构参数与电子顺磁共振(EPR)参量之间的定量关系;利用3d9离子正交(D2h)伸长八面体对称EPR参量的高阶微扰公式计算了K2Cd(SO4)2·6H2O∶Cu2+的g因子gi(i=x,y,z)和超精细结构常数Ai.研究表明,K2Cd(SO4)2·6H2O晶体中络离子[Cu(H2O)6]2+的Cu2-H2O键长分别为Rx≈0.181 nm,Ry≈0.199 nm,Rz≈0.232 nm,局域结构为沿C4轴方向呈正交伸长八面体(D2h)结构.所得EPR参量理论计算与实验符合较好,并对上述结果进行了讨论.     

ZPPH晶体中掺杂VO~(2+)的吸收光谱与EPR参量的理论研究

本文基于晶体场理论,建立了10×10阶的3d~1离子的全组态能级矩阵,由全对角化法(CDM)计算了ZPPH (ZnKPO_4·6H_2O)∶ VO~(2+)晶体的吸收光谱与顺磁g因子;同时,运用3d~1离子在C_(4v)对称下的能级公式和电子顺磁共振(EPR)参量高阶微扰(PTM)公式,计算了ZPPH∶ VO~(2+)晶体的光学吸收谱和EPR参量g因子g_(//),g_⊥和超精细结构常数A_(//),A_⊥,所得理论结果与实验符合.两种理论方法对比研究表明:对3d~1(V~(4+))电子组态,微扰法所得结果是全对角化法所得结果的一种很好近似.对所得结果的合理性进行了讨论.     

掺Cr~(3+)晶体SrLaGaO_4和Cs_2CdCl_4的EPR理论研究

根据晶体场理论,考虑到掺杂过渡金属离子的半径和价态与基质离子的差异,初步建立四角晶场中杂质离子局域结构崎变模型。并采用半自洽场d轨道模型、EPR参量高阶微扰方法、局域结构模型和点电荷模型,在强场图象中解释了掺Cr3+晶体SrLaGaO4和Cs2CdCl4的EPR谱(零场分裂参量D值以及g因子)。理论计算值与实验数据吻合较好,表明过渡金属离子局域结构伸缩模型是合理的,可运用到四角对称的其他晶体谱学特性研究。     

YAG:V2+激光材料晶格畸变及其EPR参量研究

利用Newman的晶场叠加模型,建立了晶体微观结构与电子顺磁共振(EPR)参量之间的定量关系.采用全组态完全对角化方法,对YAG:V2+晶体的局域晶格畸变及其EPR参量进行了系统的研究,结果表明:V2+离子掺入YAG晶体后,V2+离子的局域结构产生压缩三角晶格畸变,沿[111]晶轴方向V2+离子上方的三个O2-配体与下方的三个O2-配体均偏离[111]轴1.96°,从而成功地解释了YAG:V2+晶体的EPR参量.同时研究也表明,SS与SOO磁相互作用对EPR参量的贡献不可忽略.     

Al2O3:V2+晶体自旋哈密顿参量的理论解释

在考虑微小磁相互作用(包括SS、SOO和OO作用)的基础上,采用全组态完全对角化方法,建立了A l2O3晶体中V2 离子的局域结构与自旋哈密顿参量定量关系,对A l2O3:V2 晶体基态和激发态零场分裂以及基态g因子等自旋哈密顿(SH)参量给出了统一的解释。结果表明,V2 离子进入A l2O3晶体后,上下配体氧平面分别沿C3轴向远离三角中心的方向移动了0.0021nm和0.0020nm。理论计算结果与实验值符合甚好。     

Ni(en)3[Ni(en)2Ag2(NCS)6]·H2O晶体的吸收光谱和EPR谱的研究

采用半自洽场(semi-SCF) d轨道模型和点电荷模型,建立起了过渡金属离子晶体局域结构、吸收光谱与EPR谱之间的定量关系,应用高阶微扰的方法,引入平均共价因子N,统一的解释了ENST晶体中过渡金属Ni2+在D4h对称的伸长和压缩八面体时的吸收光谱、顺磁g因子和零场分裂D的值,其计算结果与实验发现较好的符合,同时本文还确定了实验中测得的零场分裂D的符号以及在实验中未测得的部分吸收光谱的值.     

Ni(IO3)2·2H2O晶体的局部结构、吸收谱和漫反射光谱的研究

采用半自洽场(semi-SCF)d轨道模型和点电荷模型,利用完全对角化方法,建立了D4h对称晶体场中晶体的局部结构与光谱之间的定量关系,统一解释了Ni(IO3)2·2H2O晶体的局部结构、吸收光谱和漫反射光谱的实验值,预测了Ni(IO3)2·2H2O晶体的光谱精细结构和电子顺磁共振(EPR)谱(零场分裂D和顺磁g因子).所得理论结果与实验值符合得很好.     

Mesomorphic Properties of the 4-(4-n-Alkoxybenzoyloxy)-Benzylidene-4-n-Alkoxyanilines and 4-(4-n-Alkoxybenzoyloxy)-3-Methoxy-Benzylidene-4-n-Alkoxyanilines

Transition temperatures, transition enthalpies and X-ray results are reported for 4-(4-n-heptyloxybenzoyloxy)-benzylidene-4-n-alkoxyanilines, 4-(4-n-nonoxybenzoyloxy)-benzylidene-4-n-alkoxyanilines and their 3-methoxy-benzylidene substituted derivatives.     

Vibrational Studies of Gel Grown Ferroelectric RbHC4H4O6 and SrC4H4O6 4H2O Crystals

Single crystals of Rubidium Hydrogen Tartrate (RbHT) and Strontium Tartrate Tetrahydrate (SrTT) have been grown by a gel technique using a chemical reaction method. A controlled reaction has been employed between tartaric acid and feed solution (RbCl for RbHT and Sr(NO₃)₂) at room temperature. The laser Raman and FT-IR spectra of these crystals are recorded in the frequency range 100 - 4000 cm^-1. The presence of tartrate ion, monohydrogen tartrate ion, water molecules and external mode vibrational frequencies are identified and discused. The doublet and broad nature of tartrate ion vibrational frequencies have also been observed and analysed.     

Na+对制备Al4SiC4/Al4O4C复合耐火材料的影响

以焦宝石、活性炭和铝粉为原料,添加Na2CO3制备Al4SiC4/Al4O4C复合耐火材料.采用化学分析、XRD和SEM等测试技术,研究了Na+对材料物相组成和显微结构的影响.结果表明:添加Na2CO3加速了Al2O3和活性炭的反应,促进了Al4O4C的生成.未添加Na2CO3时生成的Al4SiC4晶粒表面光滑,添加Na2CO3后Al4SiC4晶粒粗糙、凹凸,缺陷明显增加.此外,未添加Na2CO3的试样中生成的Al4O4C呈短纤维状,添加Na2CO3后全部转变为细小颗粒.     

New Cluster Precursors—K5 Pyramids and K4 Tetrahedra—for Self-Assembly of Crystal Structures of Mn4(ThMn4)(Mn4)-tI26, Mn4(CeCo4)(Co4)-tI26, and MoNi4-tI10 Families

Crystallography Reports - A combinatorial and topological analysis has been performed, and the self-assembly of the crystal structures of the Mn4(ThMn4)(Mn4)-tI26 (sp. gr. I4/mmm),...     

The Synthesis of Deuteriated 4-n-Alkyl-4′-Cyanobiphenyls

A single synthetic route for chain-deuteriated, totally ring-deuteriated, or per-deuteriated 4-n-alkyl-4′-cyanobiphenyls has been developed. This new route gives better yields than the previously reported route for the synthesis of 4-cyano-4′-n-pentyl-d₁₁-biphenyl and also eliminates the main “impurity” present in the final product. The synthesis of 4-cyano-4′-n-pentyl-d₁₁-2′,3′,5′,6′-tetradeuteriobiphenyl is also reported.     

X-ray Studies on the Liquid Crystalline Phases of the 4-[4-n-Heptyloxy-Benzylidene-Amino]4'-cyanobiphenyl

By means of X-ray diffraction studies of oriented and non-oriented samples the lattice parameters of the orthorhombic cell of the S_E phase as well as of the hexagonal cell of the S_B phase were determined. By packing considerations a bimolecular building unit with oppositely arranged cyano-groups was assumed in the case of the S_E phase. The S_B phase is characterized by an ABAB sequence of the smectic layers in which the molecules are hexagonal arranged. The increasing mobility of the molecules at increasing temperature offers the possibility for a part of the molecules to slide in a more stable dimerized form. In the N_R and S_A phase the existence of monomers as well as of dimers is assumed. In this way a conception of the phase transitions S_E → S_B → N_R → S_A is given on the base of a decrease by steps of the dipole-dipole repulsion.     

The Crystal and Molecular Structure of 4'-Cyanophenyl-4-n-Pentylbenzoate

The crystal and molecular structure of the title compound with the formula C₅H¹¹—C₆H₄—COO—C₆H₄—CN (CPPB) has been determined by X-ray diffraction methods. CPPB crystallizes in the monoclinic space group P2₁/n with eight molecules in a unit cell of dimensions a = 15.268(2) Å, b = 9.165(1) Å, c = 24.031(3) Å, β = 94.67(1)°. The structure has been solved by direct methods and refined to an R value of 0.070.

The CPPB molecules adopt a stretched form and are packed in an approximate parallel imbricated mode, the molecular long axes making an angle of about 5° with the crystal c axis. The molecular geometry and packing are discussed in relation to the mesomorphic behavior of CPPB.     

A Doubly Interpenetrated Layer Structure: 4-Acetamidobenzaldehyde 4-Nitrophenylhydrazone

Abstract  

The title molecule, 4-acetamidobenzaldehyde 4-nitrophenylhydrazone, is essentially planar with the maximum deviations from the least-squares plane through the 22 non-hydrogen atoms being 0.176(1) ? (nitro-O) and −0.152(1) ? (amide-O). The dihedral angle between the benzene rings is 6.93(7)°. The conformation about the C=N bond is E. The presence of amide-H···O-nitro and hydrazine-H···O-amide hydrogen bonding leads to the formation of zigzag 2-D arrays with a pseudo three-connected brick-wall network when viewed normal to the plane of the layer. The layers are sustained by 38-membered {···OCNC₅N₂C₄NO···HNCO···HN₂C₅NH···ONC₄NH} synthons and the rather large voids defined by these are occupied by a centrosymmetrically related layer to result in the formation of a doubly interpenetrated network. These stack along the b direction being connected by C–H···O interactions. The compound crystallizes in the monoclinic space group P2₁/c with a = 10.8152(3) ?, b = 10.9469(2) ?, c = 12.9198(4) ?, β = 113.679(1)°, and Z = 4.