内嵌富勒烯[M@C70] (M=Li, Na, K, Be, Mg, Ca)与[Mg(H2O)6]2+相互作用的密度泛函理论研究

使用密度泛函理论方法, 对内嵌多种碱金属及碱土金属原子(M=Li, Na, K, Be, Mg, Ca)的富勒烯C70与水合Mg(II)离子之间的相互作用进行了理论研究. 首先对各原子(M=Li, Na, K, Be, Mg, Ca)嵌入C70后的形成能进行了讨论, 之后计算了[M@C70]各体系与[Mg(H2O)6]2+的相互作用能, 并采用自然键轨道理论(NBO)研究了电荷转移的情况, 最后进行了电子密度拓扑分析. 结果表明, 内嵌原子半径越大, [M@C70]各体系的热力学稳定性就越高, 转移至[Mg(H2O)6]2+的电荷也随之增加, 二者之间的相互作用属于闭壳层相互作用及共价作用.     

重电子金属CeCu5.8 M0.2(M=Ni,Zn,Cd) 低温物性的比较

研究了不同元素等量掺杂下重电子金属CeCu5.8M0.2(M=Ni,Zn,Cd)低温电阻、比热容和磁化率随温度的变化关系.分析讨论了掺杂元素M(M=Ni,Zn,Cd)的磁性、价态及原子尺寸对近藤温度Tk、相干温度(即电阻极大值的温度TRmax)、每个Ce离子在较高温度时的平均磁矩μB以及在温度降低时被传导电子自旋屏蔽过程的影响.     

Structures and energetics of BenGen (n = 1–5) and Be2nGen (n = 1–4) clusters

Cluster geometries and energies of Be_nGe_n (n = 1–5) and Be_2nGe_n (n = 1–4) have been examined in theoretical electronic structure calculations. Structure optimisations were carried out using DFT B3LYP/6-31G(2df) and the energies of the optimum geometries were ordered in QCISD(T) calculations. Be and Ge bond to each other and to other atoms of their own kind, creating a great variety of low-energy clusters in a variety of structural types. Comparisons of the germanide clusters with previously explored silicide and carbide structures reveal some structural similarities, but the germanides have much more in common with the beryllium silicides than with the carbides. However, germanide clusters show a greater tendency to form cage-like structures with potential in technological applications.     

内嵌富勒烯[M@C_(70)](M=Li,Na,K,Be,Mg,Ca)与[Mg(H_2O)_6]~(2+)相互作用的密度泛函理论研究

使用密度泛函理论方法,对内嵌多种碱金属及碱土金属原子(M=Li,Na,K,Be,Mg,Ca)的富勒烯C70与水合Mg(II)离子之间的相互作用进行了理论研究.首先对各原子(M=Li,Na,K,Be,Mg,Ca)嵌入C70后的形成能进行了讨论,之后计算了[M@C70]各体系与[Mg(H_2O)6]2~+的相互作用能,并采用自然键轨道理论(NBO)研究了电荷转移的情况,最后进行了电子密度拓扑分析.结果表明,内嵌原子半径越大,[M@C70]各体系的热力学稳定性就越高,转移至[Mg(H_2O)6]2~+的电荷也随之增加,二者之间的相互作用属于闭壳层相互作用及共价作用.     

红色长余辉材料Y_2O_2S:Eu,Si,M(M=Mg,Ca,Sr,Ba)的制备及发光性能

采用高温固相法合成了红色长余辉材料Y2O2S:Eu,Si,M(M=Mg,Ca,Sr,Ba),利用X晶体衍射、发光光谱、热释光测量等对材料的性能进行了表征。结果分析表明:Y2O2S:Eu,Si,M(M=Mg,Ca,Sr,Ba)长余辉材料的最大荧光发射和余辉发射峰完全一致都位于627nm,产生红光发射,是典型的Eu3+离子的5D0-7F2跃迁。激发停止后,能够产生较好的余辉性能。碱土金属离子能够增强其荧光发射峰强度并对余辉性能有一定促进作用,其中以Mg2+最好,其次是Ba2+。     

M2SiO4:Re(M=Mg,Ca,Ba;Re=Ce3+,Tb3+)的发光性能

合成了系列M2SiO4∶Re(M=Mg,Ca,Ba; Re= Ce3 ,Tb3 )样品,研究了样品在真空紫外区域的激发光谱和发射光谱.从激发谱可以看出:M2SiO4∶Re(M=Mg,Ca,Ba; Re= Ce3 ,Tb3 )在147,172 nm有很强的吸收带.用Mg,Ca完全取代Ba2SiO4∶Tb3 中的Ba ,相对应的晶体的晶格参数逐渐增大,晶场的能量逐渐减少,其激发光谱随着碱土离子半径的增加向长波方向移动.在172 nm真空紫外光激发下,观察到M2SiO4∶Re(M=Mg,Ca,Ba; Re=Tb3 和M2SiO4∶Re(M=Mg,Ca,Ba; Re= Ce3 ,Tb3 )特征发射;在真空紫外激发下,随着M2SiO4∶Re(M=Mg,Ca,Ba; Re= Ce3 ,Tb3 )中Ce3 含量的增加,M2SiO4∶Re的特征发射明显减弱,并分析讨论了相关发光现象的成因.     

(XB2)2(X=Al, Be, Na, Mg)团簇的密度泛函研究

用密度泛函理论(DFT)的杂化密度泛函B3LYP方法在6-31G*基组水平上对(XB2)2(X=Al,Be,Na,Mg)团簇各种可能的构型进行几何结构优化,预测了各团簇的最稳定结构.并对最稳定结构的电子结构、振动特性、成键特性和电荷特性等进行了理论研究.结果表明,团簇的几何结构大多是平面结构,通常是B-B键和B-X键共存,较少出现X-X键.团簇的稳定结构中通常是几个呈负电性的B原子形成一个负电中心,而其他B原子和X原子处在端位,且显正电性.     

Infrared Spectroscopic Study of Td‐Type Piperazinemetal(II) Tetracyanometallate(II) Benzene(1/1) Clathrates: Cd(C4H10N2)Cd(CN)4·C6H6 and Cd(C4H10N2)Hg(CN)4·1,25 C6H6

Abstract

The title compounds have been prepared in powder form. Their spectral data have been compared with those of the corresponding host complexes and found to be consistent with the host structure found in T_d‐type clathrates.     

M_2Eu_xLn_(1-x)AlO_5(M=Ca,Sr,Ba,Ln=La,Gd,Lu)红色荧光粉发光性质的研究

用高温固相反应法合成了M_2Eu_xLn_(1-x)AlO_5(M=Ca,Sr,Ba,Ln=La,Lu,Gd)荧光粉,研究了荧光粉的发光性质。在紫外光和近紫外光激发下,样品的发射光谱由Eu~(3+)的5D0→7FJ(J=0,1,2,3,4)特征发射组成。其中Eu3+离子位于590 nm附近的5D0→7F1和位于620 nm附近的5D0→7F2跃迁发射的强度最强。荧光粉的激发光谱都是由O~(2-)-Eu~(3+)电荷迁移带和Eu~(3+)的f-f跃迁构成的。M_2Eu_xLa_(1-x)AlO_5(M=Ca,Sr,Ba)的O2--Eu~(3+)的电荷迁移带的峰位按Ca、Sr、Ba顺序向长波方向移动。研究了用La、Gd和Lu替代M_2Eu_xLn_(1-x)AlO_5中Ln的位置对样品发光的影响。给出了Eu~(3+)浓度对发光强度的影响。分析了M_2Eu_xLn_(1-x)AlO_5和M_2Eu_xLn_(1-x)AlO_5的荧光寿命。     

ODMR Study of Zn1−x Mn x Se/Zn1−y Be y Se and (Cd1−x ,Mn)Te/Cd1−y Mg y Te Diluted Magnetic Semiconductor Quantum Wells

The effects of microwave pumping with a frequency of 60 GHz on the magneto-optical properties of diluted magnetic semiconductors (DMSs) are studied in (Zn,Mn)Se/(Zn,Be)Se and (Cd,Mn)Te/(Cd,Mg)Te quantum wells. Resonant heating of the Mn²⁺ ions in the electron spin resonance conditions leads to an increase in the Mn-spin temperature, which exceeds the bath temperature by up to 5.2 K, as detected by the shift of exciton emission line and decrease of its integral intensity. Nonresonant heating mediated by free carriers is also observed through variation of the polarization degree of emission. Direct measurements of spin–lattice relaxation times for both materials using time-resolved optically detected magnetic resonance (ODMR) technique have been performed. The mechanisms of ODMR in nanostructures of DMSs are discussed.     

Structural Features of Phosphates Ca9 – xMxDy(PO4)7 (M = Zn2+ or Mg2+)

Physics of the Solid State - Phosphate solid solutions based on the whitlockite family Ca9 – xMxDy(PO4)7 (M = Zn2+ or Mg2+) have been obtained. The samples have been...     

M2CeO4(M=Ca,Sr,Ba)的结构与发光特性

SSr2CeO4是一种新型的一维结构发光材料，其特殊的结构对其发光特性有决定性的作用。Sr2CeO4体系中可以顺利地进行能量传递，产生较强电荷迁移发光。合成了M2CeO4(M=Ca,Sr,Ba），发现与Sr2CeO4具有类似结构的Ba2CeO4也可以发光，而结构完全发生了变化的Ca2CeO4则不发光。     

Optical spectroscopy and electronic structure of compounds HoNi5 − x Al x (x = 0, 1, 2)

The optical properties of the compounds HoNi_{5 ? x} Al _x (x = 0, 1, 2) have been investigated using the ellipsometric method in the wavelength range from 0.22 to 16 μm. The electronic structure of these intermetallic compounds has been calculated in the local electron-spin density approximation with the correction for strong electronic interactions in the 4f shell of the holmium ions. The experimental dispersion dependences of optical conductivity in the region of interband light absorption have been interpreted based on the results of the calculation of the electron density of states. The plasma and relaxation frequencies of electrons have been determined.     

High temperature superconductivity in (M1−xM′x)2CuO4−δ and related compounds (M = Y,La, Eu,Sm; M′ = Ba,Sr)

Compounds of the form (M_1−xM′_x)₂CuO_4−δ and related compounds where M and M′ are Y, various rare earths from La to Lu, and the alkaline earths Sr and Ba, have been investigated in connection with high temperature superconductivity. High temperature superconductivity is confirmed for the system (La_1−xBa_x)₂CuO_4−δ, (La_1−xSr_x)₂CuO_4−δ and (Y_1−xBa_x)₂CuO_4−δ with superconducting transition temperature T_c onsets of 30 K, 38 K and 90 K, respectively. We have found that the related systems (Eu_1−xBa_x)₂CuO_4−δ and (Sm_1−xBa_x)₂CuO_4−δ also exhibit high temperature superconductivity with T_c onsets of 95 K and 65 K, respectively. The highest T_c onset observed in this investigation was 97 K for a sample with the nominal composition of the spinel structure Y_0.33Ba_0.67Cu₂O_4−δ. Measurements of the specific heat C as a function of temperature T on a La_0.8Sr_0.2CuO_4−δ sample reveal a break in slope in the C/T vs T curve at the T_c midpoint, but no clearly discernable jump in C at T_c. A linear term ≈ λ′T in C was observed at low temperature in the superconducting state.     

Crystal structure and magnetic properties of pseudoternary TbRh2−xMxSi2(M = Ru,Ir) compounds

The structural and magnetic characteristics of the pseudoternary TbRh_2−xM_xSi₂(M = Ru, Ir) compounds were studied. The compounds crystallize in the tetragonal ThCr₂Si₂-type structure. The magnetic data were collected in the temperature range 70–300 K. Their magnetic susceptibilities satisfy the Curie-Weiss law in the temperatures higher than 130 K. The magnetic moment of the rare earth atom is larger than of the free Tb³⁺ ion. A modified RKKY theory with included interaction between the conduction electrons was applied to explain the variation of properties of the compounds.     

碱土金属掺杂Y_(1-x)AE_xCrO_3(AE=Mg,Ca)的物性研究

采用溶胶-凝胶法制备了名义Y_(1-x)AE_xCrO_3(AE=Mg,Ca;x=0~1/3)多晶样品,并研究其晶体结构、磁性、输运性质.Y_(0.9)Ca_(0.1)CrO_3晶格常数及晶胞体积相对于YCrO_3减小,这是Cr~(3+)由于电荷补偿机制向Cr~(4+)转变进而增大CrO~6八面体畸变程度的结果.碱土金属掺杂几乎不改变YCrO_3的反铁磁转变温度(~138K),但会导致体系有效磁矩明显降低.Y_(0.9)Ca_(0.1)CrO_3的M-H曲线呈现出未饱和的明显铁磁Loop,由体系倾斜的G型反铁磁序造成;Y_(0.9)Ca_(0.1)CrO_3输运性质呈现出lnρ与1000/T的线性相关关系,由于晶格畸变场导致的小极化子受热激活剧烈跳跃,体系电阻率随着温度升高显著降低.     

甲壳胺膜中MS(M=Cd,Zn)半导体纳米微粒形成机理的探讨

采用红外光谱（ＩＲ）和原子力显微镜（ＡＦＭ）对甲壳胺中纳米微晶生长过程进行了监测,并对测试结果进行了分析与讨论,提出甲壳胺膜中ＭＳ（Ｍ＝Ｃｄ,Ｚｎ）半导体纳米微晶可能的生长机制。同时还利用ＡＦＭ对甲壳胺中纳米微晶的形貌和尺度进行了测定。     

M-Uracil复合物(M=Ca2+和Mg2＋)特征振动的密度泛函理论分析

采用密度函数理论的B3LYP交换关联能泛函在6-311 G(2df,2p)基组水平上,对Ca2 、Mg2 与尿嘧啶(简称U)三种各互变异构体(简称U1、U2和U3)形成的复合物进行了优化计算,获得稳定复合物的构形,并对这些稳定复合物进行振动频率计算.分析计算结果发现由于离子的参与,单体分子振动的力常数和折合质量均会发生变化,导致红外振动谱线发生不同程度移动;进一步分析发现C-H和O-H键的氢原子作弯曲振动和伸缩振动的谱线移动不确定,直接与离子作用的氧原子参与的振动谱线会发生红移,不直接与离子作用的氧原子参与的振动谱线会发生蓝移.