Structure properties for the superconductor MgCNi<Subscript>3</Subscript> under high pressure with synchrotron radiation

In situ high pressure energy dispersive X-ray diffraction measurements on cubic-perovskite superconductor MgCNi₃ under pressure up to 22 GPa have been performed by using diamond anvil cell with synchrotron radiation. We have investigated its crystal structure and compressibility. The results show that the structure of MgCNi₃ is stable under pressure up to 22 GPa. According to Birch-Murnaghan state equation, when we assume B ₀′ = 4, we get B₀ = 267.8 ± 7.2 GPa.     

Discovery of C<Subscript>4</Subscript> species at high altitude in Qinghai-Tibetan Plateau

Plant specimens are collected from the areas between latitude 27°?2′N and 40°57′N, and longitude 88°93°E and 103°24′E, with an altitudinal range from 2210 to 5050 m above the sea level in Qinghai-Tibetan Plateau. The stable carbon isotope analysis indicates that two of Chenopodiaceae and six of Poaceae in the samples are C4 plants. Four of the C4 plants are found in 11 spots with altitudes above 3800 m, and Pennisetum centrasiaticum, Arundinella yunnanensis and Orinus thoroldii are present in six spots above 4000 m, even up to 4520 m. At low CO2 partial pressure, that sufficient energy of high light improving C4 plant's tolerance of low temperature and precipitations concentrating in growing season probably are favorable for C4 plants growing at high altitude in Qinghai-Tibetan Plateau.     

Phase transition and thermodynamic properties of BaS: An <Emphasis Type="Italic">Ab initio</Emphasis> study

The hydrostatic-pressure-induced transition phase of BaS from the NaCl-type structure (B1) to the CsCl-type structure (B2) is investigated by ab initio plane-wave pseudopotential den-sity functional theory method. It is found that the transition pres-sure from B1 to B2 phases is 8.2 GPa according to the usual con-dition of equal enthalpy. Through the quasi-harmonic Debye model,the dependences of the relative volume V/V0 on the pres-sure P,the thermal expansion parameter ratio on pressure P,and the Debye temperature Θ and heat capacity CV on pressure P and temperature T are estimated.     

Long-chain alkenones in sulfate lakes and its paleoclimatic implications

Long-chain alkenones are ubiquitous in marinesediments. The relationship between alkenone unsatura-tion and temperature has been proved by field studies andcultures of E. huxleyi[1] and G. oceanica[2]. As an idealproxy for sea surface paleotemperature estimation, theU37 index is widely applied to reconstructing paleotem- K 'perature in most oceanographic settings[3—10]. The suc-cessful progresses in the ocean invoked the researchers’attention to the study of LCAs in the liminic system.Cr…     

Compressibility of a natural kyanite to 17.5 GPa

The compressional behaviour of a natural kyanite, (Al_1.99Fe_0.01)SiO₅, has been investigated to about 17.5 GPa at 300 K using a diamond-anvil cell and synchrotron X-ray diffraction. The pressure–volume data fitted to the third-order Birch–Murnaghan equation of state (EoS) yield an isothermal bulk modulus (K_0T) of 192 ± 6 GPa and pressure derivative () of 6 ± 1. When is fixed as 4, the derived K_0T is 201 ± 2 GPa. These values are in excellent agreement with most experimental determinations in the literature. Consequently, it can be concluded that the compressibility of kyanite under high pressures has been accurately constrained.     

Synthesis, crystal structure and properties of binuclear manganese complex [(bipy)2Mn2(μ-O)(μ-Ac)2(H2O)2](ClO4)2

Binuclear manganese complex [(bipy)₂Mn₂(μ-O)(μ-Ac)₂(H₂O)₂](ClO₄)₂ was synthesized by the reaction of MnAc₃ · 2H₂O with 2,2′-bipyridine in the HAc-NaAc buffer (pH = 4.0). X-ray diffraction result for the single crystal shows that the crystal is monoclinic, space group C₂/C, with a = 3.408 2(7),b = 0.864 4(2),c = 2.174 9(4) nm, β= 105.2∘, V=6.186(2) nm³, Z= 8. There are two very strong peaks of UV-Vis spectrum in the range of 400–600 nm, which are similar to those of Mn catalase and Mn ribonuleotide reductase extracted from organisms. Cyclic voltammogram shows that the complex in CH₃CN undergoes quasi-reversible one-electron reduction and oxidation at E_1/2=1.15V.     

Resonance-enhanced multiphoton ionization spectroscopy on the B′2Σ+ and B2Π states of NS

Resonance-enhanced multiphoton ionization （REMPI） spectra of N^32S and N^34S have been recorded in the range of 35700-40200 cm^-1. The radical was generated by a pulsed dc discharge of a mixture of SF6 and N2 under a supersonic free jet condition. All the 16 observed bands of N^32S radicals have been assigned, among which 12 bands belong to three transition progressions （v′=0-4, 0）, （v′=1-4, 1） and （v′=2-4, 2） from the X^2П ground state to the B′^2∑^＋ upper state and the rest correspond to （9, 0）, （10, 0）, （11, 0） and （12, 0） bands of B^2П-X^2П transition, respectively. Analysis of the rotationally resolved spectra yields exhaustive spectroscopic constants of both the X^2П ground state and the B′^2∑^＋ excited state. The electronic transition bands of the isotopic molecule N^34S have been rotationally analyzed for the first time and the rotational constants of the ground and upper states have been determined simultaneously.     

Synthesis and light-emitting properties of organic electroluminescent compounds and their metal complexes

Several organic electroluminescent (EL) compounds, 2,2‘-(1,4-phenylenedivinylene)bis-3,3-dimethyl-indolenine (1), 2,2‘-(1,4-phenylenedivinylene)bis-benzoxazole (2), 2,2‘-(1,4-phenylenedivinylene)bis-benzothiazole (3), 4,4‘-(1,4-phenylenedivinylene)bis-quinoline (4), 2,2‘-(1,4-phenylene divinylene)bis-quinoline (5), 2,2‘-(1,4-phenylenedivinylene)bis-1,3,3-trimethyl-indolenine dichlo ride (6), 2,2‘-(1,4-phenylene-divinylene)bis-1-hydro-3,3-dimethyl-indolenine dichloride (7), 2,2‘-(1,4-phenylenedivinylene)bis-8-acetoxy-quinoline (8), 2,2‘-(1,4-phenylenedivinylene)bis-8-hydroxyquinoline (9) and metal complexes of 9, Al(PHQ) (10) and Zn(PHQ) (11), have been synthesized and characterized. The crystal structure of 6 was determined. Light emitting properties of the prepared compounds have been investigated. 1 produces an orange-yellow emission (λmax=575nm). The cation, 6, gives a red emission (λmax=607nm), which is shifted 32 nm to the red compared to 1.8 produces a yellow emission (λmax=567nm). The metal complex 10 gives a red emission (λmax=610nm), which is a red shift of 43 nm compared to 8. The change in structure in the prepared compound caused a change in the electron distribution in the compounds, which induces a large wavelength shift of the emitted-light. Thermal analysis showed that the decomposition temperatures of the metal complexes (10, 11) were higher than those for the smaller organic molecular compounds (1-9). Therefore, metal complexes (10, 11) can be used as EL materials over a larger temperature range.     

Calculation method of electronic structure and its application to (I h andI) fullerenes

A new calculation method was discussed to treat the Hückel Hamiltonian of any fullerene with a certain point group symmetry. This method was applied to calculating the electronic energy levels of icosahedral fullerenes C\-n(I\-h: n=60h 2, 0相似文献   

Monte Carlo simulations for two-dimensional Ising system far from equilibrium

With a dynamic Monte Carlo simulation, which is free of critical slowing down, the critical behavior of two-dimensional Ising model at non-equilibrium states is investigated. We focus on the two-time autocorrelation function A(t, t' ) to identify the dynamic exponent z in two different evolution stages, quenched from a high temperature state and a completely ordered state to the critical state at TC, re-spectively. By using the heat-bath algorithm, the dynamic critical exponent is estimated as z ≈ 2.16. As a result, the universality of the scaling behavior is verified numerically, and the exponent λC is deter-mined complete by λC = β /ν for the evolutions from an initial completely ordered state.     

The fourier transformations of positive distributions on lorentz groupSO (3, 1)

With the aid of Plancherel-Godement Theorem, we prove that every positive distributionT onSO (3, 1) which is bi-invariant underSO(3) corresponds to a measure μ on ω=∝σC|s(2-s)>=0∝, and μ can be decomposed intoμ=μ ₁+μ ₂, whereμ ₁ is a bounded measure on 0<=s<=2 andμ ₂ is slowly increasing measure on (sχC|Re(s)=1)} Foundation item: Supported by the National Natural Science Foundation of China (19871065) and Hua Cheng Mathematics Science Foundation. Biography: Zhu Li (1976-), male, Graduate student, research interest: partial differential equation     

几类图的符号星控制数

给出Km×Cn,Cm×Cn,Km×Kn这三类图的符号星控制数.     

Chaos in the sense of Li-Yorke and the order of the inverse limit space

Let I= [0,1] and ω0 be the first limit ordinal number. Assume that f: I→I is continuous , piece-wise monotone and the set of periods of f is { 2': i∈ {0} ∪ N}. It is known that the order of (I, f) is ω0 or ω0 + 1. It is shown that the order of the inverse limit space (I, f) is ω0 (resp. ω0 + 1) if and only if f is not (resp. is) chaotic in the sense of Li-Yorke.     

High-pressure sound velocity of perovskite-enstatite and the possible composition of the Earth’s lower mantle

The compressional sound velocity V_p for enstatite of polycrystalline specimens were measured at pressures from 40 to 140 GPa using the optical analytical techniques under shock loading. The dependence of V_P, (in km/s) on Hugoniot pressure (P, in GPa) can be described by InV_p= 3.079-0.691 In(P) + 0.094(lnP)². V_p satisfies Birch’s law:V _p = 4.068 + 1.677_ρ, where ρ is corresponding density, which indicated that enstatite is stable throughout the conditions of the lower mantle. The wave velocityP is 0.5% lower and the wave velocity S is 2% higher than that of PREM respectively. We concluded that the lower mantle is mainly composed of perovskite-(Mg_1-x, Fe_x) SiO₃ and only a small amount of (Mg_1-x, Fe_x) O is allowed in it.     

Orientational domains at room temperature in La0.33Ca0.67MnO3 perovskite

Orientational domains at room temperature in orthorhombic perovskite La_0.33Ca_0.67MnO₃ were studied by group-theory and observed systematically using transmission electron microscopy. There are six orientational variants (A, A′, B, B′, C andC′) in orthorhombic perovskite La_0.33Ca_0.67MnO₃. Their orthorhombicb _o directions are parallel to thea _p,b _p andc _p directions of the cubic prototypic perovskite, respectively. In each case there are two orientational variants (e.g.,A andA′) with theira _o andc _o axes interchanged. Among the possible 15 boundaries between these 6 variants there are only two types of domain boundaries: (1) m<100>boundariesC′/C, A′/A, andB′/B. (2) m<110>boundaryiesC′/A, C′/A′, C′/B, C′/B′, C/A, C/A′, C/B, C/B′, B′/A, B′/A′, B/A, andB/A′. Foundation item: Supported by the National Natural Science Foundation of China (19974031) and US DOE(DE-AC02-98CH10886) Biography: WANG Ren-hui (1937-), male, Professor.     

Crystal structure and magnetism of the binuclear Gd(III) complex Gd2(C12H8N2)2(C6H5COO)6

In the medium of H₂O, C₂H₅OH and HAC, the reaction of Gd(NO₃)₃·6H₂O with C₆H₅COONa and C₁₂H₈N₂ produced a novel binuclear Gd(III) complex in formula [Gd₂(C₁₂H₈N₂)₂ (C₆H₅COO)₆]. Crystallographic data: crystal system, triclinic; space group, P1; unit cell dimensions, a=1.191 9(2) nm,b =1.244 2(2) nm,c = 1.080 4(2) nm, α = 93.57(3)°, β= 113.33(3)°, γ= 105.06(3)°, Z=l. The finalR =0.037 6. The magnetic measurement of the crystal powder in the temperature region of 1.5–300 K shows that this complex possesses antiferromagnetic property with fitting magnetic parametersJ = −0.471 andg =1.975.     

Dependence of nitrogen concentration in type Ib diamonds on synthesis temperature

Type Ib diamonds were grown by the temperature gradient method (TGM) at 5.5 GPa and 1500－1560 K in a china-type cubic anvil high pressure apparatus using Ni₇₀Mn₂₅Co₅ alloy as solvent/catalyst. The concentration of nitrogen (C_N) in type Ib diamonds synthesized at different synthesis temperatures was measured by a Fourier transform infrared (FTIR) spectrometer. The dependence of C_N in diamond on synthesis temperature was studied. For the type Ib diamonds synthesized using Ni₇₀Mn₂₅Co₅ as catalyst, its C_N decreases along with the increase of synthesis temperature.     

An experimental study of dehydration melting of phengite-bearing eclogite at 1.5―3.0 GPa

Dehydration melting experiments were performed on ultrahigh-pressure eclogite from Bixiling in the Dabie orogen at 1.5--3.0 GPa and 800--950℃ using piston cylinder apparatus. The results show that （1） eclogite with -5% phengite started to melt at T≤800--850℃ and P = 1.5--2.0 GPa and produced about 3% granitic melt; （2） the products of dehydration melting of phengite-bearing eclogite vary with temperature and pressure. Fluid released from dehydration of phengite and zoisite leads to partial melting of eclogite and formation of plagioclase reaction rim around kyanite at pressures of 1.5--2.0 GPa and temperatures of 800--850℃; （3） phengite reacted with omphacite and quartz and produced oligoclase, kyanite and melt at elevated temperatures. Oligoclase is the primary reaction product produced by partial melting of phengite in the eclogite; and （4） the dehydration melting of phengite-bearing eclogite at pressures of 1.5--3.0 GPa and temperatures ≥900℃ results in formation of garnets with higher molar fraction of pyrope （37.67 wt.%--45.94 wt.%）. Potassium feldspar and jadeite occur at P = 2.4--3.0 GPa and T≥900℃, indicating higher pressure and fluid-absent conditions. Our results constrain the solidus for dehydration melting of phengite-bearing eclogite at pressures of 1.5--3.0 GPa. Combining experi- mental results with field observations of partial melting in natural eclogites, we concluded that phengite-bearing eclogites from the Dabie-Sulu orogen were able to partially molten at P= 1.5--2.0 GPa and T= 800--850℃ during exhumation. The ultrahigh-high pressure eclogites would have experienced partial melting in association with metamorphic phase transformation under different fluid conditions.     

Quantum chemical studies on tuning the second-order nonlinear optical molecular switching of triarylborane derivatives

In this work, density functional theory (DFT) combined with the finite field (FF) method has been adopted to analyze the second-order nonlinear optical (NLO) properties of the triarylborane (TAB) derivatives obtained by introducing different inductive electron groups into the phenylene ring of the TAB (RTAB, where R=2-C6H5-C2B10H10(1),R=F(2), R=Me(3),R=NO2(4),R=NH2(5)). The static first hyperpolarizabilities (βtot) of the RTAB molecules can be switched by binding one F- to the boron center (RTAB′) or one-electron reduction (RTAB"). The DFT-FF calculations show that the βtot values of 2′, 3′ and 5′ decrease while those of 1′ and 4′ increase compared with the values of their neutral molecules, which was attributed to the fact that the charge transfers of 2, 3 and 5 become smaller and those of 1 and 4 become larger by binding one F- ion to the boron center, according to time-domain DFT (TD-DFT) analysis. However, the incorporation of one electron enhances the second-order NLO properties of the RTAB molecules remarkably, especially for system 1. It is notable that the βtot value of reduced form 1″ is 508.69×10-30 esu, i.e. about 578 times larger than that of system 1. Frontier molecular orbital (FMO) and natural bond orbital (NBO) analyses suggest that the reversal of the charge distribution between the neutral molecules and their reduced forms leads to low HOMO-LUMO energy gaps (E0) and thus large βtot values for the reduced forms.     

Compression behavior and equation of state of Ni77P23 amorphous alloy

The compression behavior of Ni77P23 amorphous alloy is investigated at room temperature in a diamond-anvil cell instrument using insitu high pressure energy dispersive X-ray diffraction with a syn- chrotron radiation source. The equation of state is determined by fitting the experimental data accord- ing to Birch-Murnaghan equation: -ΔV/V0=0.08606P-3.2×10-4P2 5.7×10-6P3. It is found that the structure of Ni77P23 amorphous alloy is stable under pressures up to 30.5 GPa.