First-Principles Prediction of High-Pressure Phase of CaC6

The lattice dynamics of rhombohedral GaG6 is studied as a function orpressure to probe Its high pressure phase with low superconducting transition temperature using the density functional liner-response theory. The pressureinduced phase transition in CaC6 is attributable to the softening transverse acoustic （TA） phonon mode at the zone boundary X （0.5, 0.0, 0.5） point. The high pressure phase is then explored by performing fully structural optimization in the supercell which accommodates the atomic displacements corresponding to the eigenvectors of the unstable mode of TA（X）. The high-pressure phase is predicted to be a monoclinic unit cell with space group P21/m.     

Jahn-Teller Distortions Cooperating with Magnetic Interaction in the Raman Spectra of La0.75Ca0.25MnO3 Thin Film

Remarkable changes (additional peaks, frequency shift, and peak width) of Raman spectra ofa La0.75 Ca0.25MnO3 thin film have been observed during the paramagnetic insulator-ferromagnetic metal transition. The vl band (230cm^-1) hardens by lattice contraction as a result of the rearrangement of Mn06 octahedra. The Jahn-Teller distortions seem to be responsible for the broadening of v2 band (485 cm^-1) above the magnetic transition temperature Tc. It is proposed that the 438cm-1 vibration mode activated in the magnetic ordering state is associated with the rearrangement of MnO6 octahedra. The softening of v3 band (610cm^-1) below TC can be ascribed to the magnetic interaction that brings into spin-phonon coupling terms.     

ICP-AES同时测定高纯碲中钙、铈和钛

ICP-AES法测定高纯碲中的杂质元素Ca、Ce和Ti,进行了碲基体影响、加标回收和精密度实验研究。加标回收率为92%—93%,相对标准偏差小于1%,所得结果令人满意。     

ICP-AES测定工业用氢氧化钠中Fe、Si、Ca和Mg

电感耦合等离子体-原子发射光谱法(ICP-AES)同时测定了工业用氢氧化钠中Fe、Si、Ca、Mg,探讨了功率对测定结果的影响,用离峰扣背景法消除背景干扰,用基体校正系数消除基体干扰,加标回收率在97.9%—105%之间。     

掺钙、钡苯甲酸铕配合物的红外光谱和荧光性能

将苯甲酸钠分别加入到氯化钙和氯化铕以及氯化钡和氯化铕混合溶液中反应,制备了苯甲酸铕-钙和苯甲酸铕-钡两个系列的三元固体配合物,其化学组成式为（Eu1-xCax）L3-x和（Eu1-xBax）L3-x（其中L为苯甲酸根,x=0～1．0）,研究了它们的红外光谱和荧光性能。由红外数据表明,配合物中对称和反对称伸缩振动吸收峰发生了分裂,而且羧基伸缩振动随钙离子（钡离子）含量的增加发生规律性变化。荧光光谱实验结果表明,在一定范围内,用不发光的钙离子或者钡离子取代苯甲酸铕中部分Eu^3＋离子,可以使Eu^3＋离子的特征荧光发射增强,表明碱土金属可以敏化Eu离子。     

La0.67Pb0.33MnO3的磁性及输运特性

利用固相反应烧结法制备了La067Pb033MnO3单相多晶样品.研究了其结构、磁性及输运特性.结果表明，样品呈菱面相晶体结构，空间群为R3C，居里温度TC(=353K)非常接近TMI(=360K).在居里温度附近，发生铁磁-顺磁转变，导电特性由金属特征向半导体特征过渡.磁电阻在居里点达到极大值.当H=16T时，磁电阻的极大值为145%；当H=08T时，磁电阻的极大值为9%.输运性质表明，TTMI时 关键词： 磁电阻 输运特性 磁极化子 钙钛石     

ICP-AES同时测定混合矿物素中的磷、钙、铁、铜、锌、锰、镁、钴

采用ICP－AES法测定混合矿物素中的磷、钙、铁、铜、锌、锰、镁、钴元素含量，并对样品的溶解酸和酸用量、元素分析线的选择以及共存元素间的干扰进行了研究。该法简便、快速，精密度和准确度较好。     

Ground-State Properties of Ca Isotopes and the Density Dependence of the Symmetry Energy

A relativistic mean field model is used to study the ground-state properties of neutron-rich nuclei in Ca isotopes. An additional isoscalar and isovector nonlinear coupling has been introduced in the relativistic mean field model, which could soften the symmetry energy, while keep the agreement with the experimental data. The sensitivity of proton and neutron density distributions and single particle states in Ca isotopes to the additional isoscalarisovector nonlinear coupling term is investigated. We found that the binding energies, the density distributions of single particle levels are strongly correlated with the density dependence of the symmetric energy in nuclear matter.     

Application of Electron-Shelving Detection via 423 nm Transition in Calcium-Beam Optical Frequency Standard

A new scheme of small compact optical frequency standard based on thermal calcium beam with application of 423 nm shelving detection and sharp-angle velocity selection detection is proposed. Combining these presented techniques, we conclude that a small compact optical frequency standard based on thermal calcium beam will outperform the commercial caesium-beam microwave dock, like the 5071 Cs clock （from Hp to Agilent, now Symmetricom company）, both in accuracy and stability.