Ligand-controlled First Hyperpolarizabilities of a Series of Tetrahedral Iridium Clusters Ir4（CO）9L： a TDDFT Study

A series of tetrahedral iridium carbonyl clusters coordinated by systematically varied series of ligands have been studied by TDDFT method focusing on their electronic and non- linear optical properties. The clusters of Ir4（CO）12 （1）, Ir4（μ-CO）3（CO）9 （2）, Ir4（μ-L）（CO）10 （L = dppm 3, dppe 4, （Ph2P）2CHMe 5, Ph2P（CH2）3PPh2 6） and Ir4（CO）10（phen） （phen = 1,10-phen- anthroline） （7） exhibit the first static hyperpolarizabilities of medium magnitude （βtot-10×10^-30 esu）. The second order nonlinear optical response of the seven clusters increase from 0 to 23 ×10^-30 esu; the high symmetric cluster Ir4（CO）12 debases its symmetry and presents the second order nonlinear optical behavior as the coordination style of some carbonyls changes to bridge style, and then the response increases regularly with the systematical variation of the ligands. The origination of the first hyperpolarizability is discussed by the expanded orbital decomposition scheme. The results suggest the d-d electron transition from the apical iridium atom to the other three Ir atoms inside the metal skeleton, and d-πelectron transitions from metals to carbonyls are responsible for the first hyperpolarizabilities. Particularly, for cluster 7, the charge transfer from d orbitals of iridium to π＊ orbirals of phenanthroline originates the first hyperpolarizabilities.     

A note on maximizing the permanent of a positive definite hermitian matrix,given the eigenvalues ∗

As a step toward understanding the unsolved problem of determining how large the permanent of a positive semi-definite matrix can be, given the eigenvalues, we note that a necessary condition for A to be a permanent maximizing matrix is that A commute with its permanental adjoint.     

Theoretical Studies on the Binding of Cd~（2＋） to Uracil and Its Thio-derivatives

The interaction of Cd2+ with uracil,2-thiouracil,4-thiouracil and 2,4-dithiouracil have been investigated by the density functional theory(DFT) calculations.For uracil and 2,4-dithiouracil,where the two basic sites are the same,Cd2+ attachment to the heteroatom at position 4 is preferred.However,for the systems where both types of basic centers,a carbonyl and a thiocarbonyl groups,are present,Cd2+ association with sulfur is favorable.The enhanced stability of these enolic and thiol forms comes from Cd2+ interaction with two basic sites simultaneously,which thereby triggers a significant aromatization of the ring.More significantly,the Cd2+ binding energy with uracil and its thio-derivatives is larger than the tautomerization barriers connecting the diketo-like forms with the corresponding enolic-like tautomers.Consequently,when associated with Cd2+,all tautomers are energetically accessible and should be observed in the gas phase.     

A note on maximizing the permanent of a positive definite hermitian matrix, given the eigenvalues

As a step toward understanding the unsolved problem of determining how large the permanent of a positive semi-definite matrix can be, given the eigenvalues, we note that a necessary condition for A to be a permanent maximizing matrix is that A commute with its permanental adjoint.     

Thermal investigations of reactive powder mixtures as precursors for melt-processing of YBa2Cu3O7−x

DTA and XRD measurements were carried out with reactive precursors taken from the YO_1.5-BaO-CuO system in order to investigate mechanisms of YBa₂Cu₃O_7–x formation. The reactions taking place depend strongly on phase composition, phase purity, powder size and heating rate. Among the examined reactive precursors a mixture of 7Y₂O₃+22BaCuO₂+10CuO turned out as the most suited for melt-processing.     

一水甲酸锂晶体二阶非线性光学系数的理论计算

采用有限场方法和含时耦合微扰方法,在6-31+G*基组水平上并考虑了电子相关效应和色散效应的影响,计算了一水甲酸锂晶体的宏观二阶非线性光学极化率和二阶非线性光学系数。其中非线性光学系数d31和d32与Roberts报道的相符,而另一个系数d33则比文献值大。计算结果还表明,在非共振情况下,电子相关效应对非线性光学极化率的影响远远超过了色散效应,同时表明Roberts报道的非线性光学系数比Singh等人报道的更为合理。     

LAP晶体二阶NLO响应电子起源理论研究

L-精氨酸磷酸盐(L-Arginine Phosphate Monohydrate, LAP)晶体，是一种有应用潜力的无机－有机杂化NLO晶体材料[1, 2]。Eimerl等人认为LAP晶体二阶NLO响应主要源于L-精氨酸分子(Arg )，磷酸根(H2PO4－)对LAP晶体宏观NLO响应没有重要贡献[2]；而许东等人认为，LAP晶体的NLO响应是由L-精氨酸分子和磷酸根共同贡献的结果[1]。本通讯通过第一原理从头算计算，揭示了LAP晶体二阶NLO响应的电子起源。 表1. 激发态性质 Table 1. The Excited States at CIS/STO-3G Level (Dmge in Debyes; l in nm; (rx)ge in au) States…     

Coupling of mixed finite elements and boundary elements

The symmetric coupling of mixed finite element and boundaryelement methods is analysed for a model interface problem withthe Laplacian. The coupling involves a further continuous ansatzfunction on the interface to link the discontinuous displacementfield to the necessarily continuous boundary ansatz function.Quasi-optimal a priori error estimates and sharp a posteriorierror estimates are established which justify adaptive mesh-refiningalgorithms. Numerical experiments prove the adaptive couplingas an efficient tool for the numerical treatment of transmissionproblems.     

158A GeV/c Pb+Pb碰撞可能有QGP的一旁证

用不含QGP假设的强子和弦级联模型(JPCIAE) ,研究了CERNWA98实验组新近发表的158 AGeV/c Pb+Pb中心碰撞中直接光子和π⁰粒子的横动量分布:两者的理论结果均一致的低于实验值.联系到JPCIAE能成功解释无直接光子超出确切迹象的WA80和WA93对200A GeV/c S+Au中心碰撞测量得出的结果:因而为158A GeV/c Pb+Pb中心碰撞中可能有QGP生成提供了一个旁证.