点缺陷浓度对非化学计量比L12型结构的A13Sc弹性性能的影响

采用密度泛函理论与Wagner-Schottky热力学模型计算了金属间化合物L1₂-A1₃Sc中点缺陷浓度与温度、成分间的关系. 结果表明: 在考察的温度区间(T=300-1200 K), 理想化学计量比L1₂-A1₃Sc中的点缺陷主要为Al空位和Sc空位, 且缺陷浓度较低(在1200 K时仅约为10^-6). 当L1₂-A1₃Sc偏离化学计量比成分时, 富Al成分端的点缺陷主要为Al反位与Sc空位, 且两种缺陷的浓度相当; 富Sc成分端的点缺陷则主要为Sc反位. 利用超胞模型进一步计算了含点缺陷L1₂-A1₃Sc晶体的弹性常数, 并计算预测了点缺陷形式和浓度对其弹性性能的影响. 结果表明: 在理想化学计量比成分附近, 点缺陷的引入均会降低非化学计量比L1₂-Al₃Sc晶体的杨氏、剪切和体积弹性模量, 增加非化学计量比L1₂-Al₃Sc弹性性能的各向异性, 但是对其脆-韧性的影响不大.     

Piezoelectric polarization and quantum size effects on the vertical transport in AlGaN/GaN resonant tunneling diodes

In this work,the electronic properties of resonant tunneling diodes(RTDs) based on GaN-AlxGa(1-x)N double barriers are investigated by using the non-equilibrium Green functions formalism(NEG).These materials each present a wide conduction band discontinuity and a strong internal piezoelectric field,which greatly affect the electronic transport properties.The electronic density,the transmission coefficient,and the current–voltage characteristics are computed with considering the spontaneous and piezoelectric polarizations.The influence of the quantum size on the transmission coefficient is analyzed by varying GaN quantum well thickness,Al_xGa_(1-x)N width,and the aluminum concentration x_(Al).The results show that the transmission coefficient more strongly depends on the thickness of the quantum well than the barrier;it exhibits a series of resonant peaks and valleys as the quantum well width increases.In addition,it is found that the negative differential resistance(NDR) in the current–voltage(I–V) characteristic strongly depends on aluminum concentration xAl.It is shown that the peak-to-valley ratio(PVR) increases with xAlvalue decreasing.These findings open the door for developing vertical transport nitrides-based ISB devices such as THz lasers and detectors.     

高能核–核碰撞Drell–Yan过程K因子常数性的研究

在高能核–核碰撞Drell-Yan过程考虑湮没项和康普顿散射项的基础上,利用双重Q²重标度模型,分别计算了碳、钙、铁、锡与其自身的核–核碰撞.结果表明,对于不同的x₁值,K因子随x₂的变化很不相同;同时,K因子变化的幅度是随核素A不同而发生微弱变化的,在特定的x₁,x₂取值有限范围内它不能近似取为常数.计算结果与实验的对比是对所用模型及QCD理论适用性的一种检验.     

Optimal configuration for vibration frequencies in a ring of harmonic oscillators: The nonidentical mass effect

The parameter diversity effect in coupled nonidentical elements has attracted persistent interest in nonlinear dynamics. Of fundamental importance is the so-called optimal configuration problem for how the spatial position of elements with different parameters precisely determines the dynamics of the whole system. In this work, we study the optimal configuration problem for the vibration spectra in the classical mass–spring model with a ring configuration, paying particular attention to how the configuration of different masses affects the second smallest vibration frequency (ω₂) and the largest one (ω_N). For the extreme values of ω₂ and ω_N, namely, (ω₂)min, (ω₂)max, (ω_N)min, and (ω_N)max, we find some explicit organization rules for the optimal configurations and some approximation rules when the explicit organization rules are not available. The different distributions of ω₂ and ω_Nare compared. These findings are interesting and valuable for uncovering the underlying mechanism of the parameter diversity effect in more general cases.     

二维相关荧光光谱探究土壤富里酸亚组分的质子键合多相性

利用同步荧光光谱（SFS）结合二维相关光谱（2D COS）和修正Stern-Volmer模型探究了森林土壤富里酸（FA）亚组分的质子键合多相性。利用XAD-8吸附树脂结合Na₄P₂O₇缓冲溶液逐步洗脱方法成功将土壤FA分级为异质性低的FA亚组分（FA₃-FA₁₃）。FA₃-FA₁₃含有类蛋白（类酪氨酸和类色氨酸）、类富里酸和类腐殖酸组分，且FA₇-FA₁₃比FA₃和FA₅含有更多含量的类蛋白组分。FA₃-FA₁₃中不同荧光组分的光谱峰强受溶液碱性pH值变化的影响较为明显。FA₃-FA₁₃的2D COS同步和异步相关谱图中自峰和交叉峰的复杂分布与荧光组分的质子键合多相性有关。FA₅-FA₁₃中类蛋白、类富里酸和类腐殖酸组分因pH值变量扰动而产生的光谱变化方向相同。在碱性pH值条件下，修正Stern-Volmer模型定量拟合FA₃-FA₁₃中荧光组分的解离常数（pK_a值），其中类酪氨酸、类色氨酸、类富里酸和类腐殖酸的pK_a值范围分别为6.11，8.93～10.12，9.32～10.65和9.70～10.63（R>0.854）。FA₃中类酪氨酸组分的低pK_a值（6.11）表明类酪氨酸组分含有更多含量的芳香族结构和相邻酚基官能团。FA₃-FA₁₃中类色氨酸、类富里酸和类腐殖酸组分的相似pK_a值（8.93～10.65）与羟基苯和氨基酸的pK_a值（8.0～12.02）相近，表明类色氨酸、类富里酸和类腐殖酸组分具有相似的质子亲和力，且酚基官能团和氨基酸组分在其质子键合过程中起主要作用。FA₃-FA₁₃中特定波长处荧光组分的波长连续变化顺序与其pK_a值递增趋势相一致，且质子结合位点的多相性特征同时存在于FA亚组分的不同荧光组分间和相同荧光组分内。FA₃中特定波长处类酪氨酸和类色氨酸组分的pK_a值（6.11～9.16）小于类腐殖酸组分（9.70～9.97），且荧光组分的递增趋势与波长连续变化的顺序（250 nm→275 nm→425～490 nm）相一致。FA₅-FA₁₃中特定波长处类色氨酸组分、类富里酸和类腐殖酸组分的pK_a值递增趋势与波长连续变化的顺序表现出相一致的规律：275 nm（8.93～9.70）→375～495 nm（9.88～10.16）→350 nm（10.65）（FA₅和FA₇），275 nm（10.11）→290～400 nm（10.35）（FA₉）和265～345 nm（9.32～9.80）→360～450 nm（10.06～10.13）（FA₁₃）。同时，FA₁₃中同一类富里酸组分的波长和pK_a值存在325 nm（9.32）→375～425 nm（10.06～10.13）的连续变化顺序。SFS-2D COS结合修正Stern-Volmer模型具有降低光谱重叠率和捕获光谱波长连续变化的优势，为深入研究有机质和污染物间复杂相互作用提供支撑。     

Influence of Density-Dependent Coupling Constants on Equation of State of Infinite Symmetric Nuclear Matter

In the mean field approximation of nonlinear relativistic σ-ω-ρ model, we have studied the influence of density-dependent coupling constants between nucleons and mesons on the equation of state (EOS) of infinite symmetric nuclear matter in different conditions. We find that the EOS of nuclear matter will become stiffer as c, d in the self-interaction of σ meson increase when the coefficients except a_ω in Γ_ω, in which the opposite occurs, are fixed. On the other hand, greater values of a_σ, b_σ, c_σ, a_ω, d_ω and smaller values of d_σ, b_ω, c_ω will lead to stiffer EOS if c and d are fixed. Besides, greater values of Γ _σ,ω lead to stiffer EOS in high density region for the EOS with same incompressibility coefficient at saturation density.     

利用单油包裹体的显微荧光和红外光光谱联合识别原油的气洗和水洗作用

采集已报道具有规模气洗作用和水洗作用的油气田岩样制成流体包裹体薄片,进行单油包裹体的显微荧光光谱和傅里叶红外光光谱测试,分别研究了遭受气洗作用和水洗作用后捕获的油包裹体的显微荧光和红外光光谱的变化规律特征,总结了两者的变化差异性。气洗导致原油光谱参数QF₅₃₅值向减值和增值方向分别扩大,CH₂/CH₃分布值范围未发生明显扩大,而峰值被平均化,H₂O/Alkanes比值分布无变化。水洗导致原油的QF₅₃₅值向增值方向扩大,CH₂/CH₃分布范围发生了明显的增移,H₂O/Alkanes明显增加。针对轻质油藏气洗后QF₅₃₅变化不明显以及中重质油藏水洗后CH₂/CH₃变化不明显的特点,首次总结出针对轻质油藏和中重质油藏的水洗和气洗作用的油包裹体光谱参数分布趋势鉴别图版。该研究对利用流体包裹体进行成藏期次精细划分和油气成藏过程恢复具有重要实际意义。     

Interacting Stoner–Wohlfarth behavior in hysteresis curves of Sm(CoFeCuZr)z magnets

Several magnets with different Zr contents were studied: Sm(Co_balFe_0.2Cu_0.1Zr_x)₈ (bal=balance; x=0, 0.02, 0.04, 0.06 and 0.08). The microstructure of the magnets includes three main phases, all crystallographically coherent: the cell phase Sm₂(Co,Fe)₁₇, the cell boundary phase Sm(Co,Cu)₅ and a lamellar Zr-rich phase, rhombohedral (ZrSm)₁Co₃. The hysteresis curves were compared with the Callen, Liu and Cullen (CLC) modification of the Stoner–Wohlfarth model for an isotropic distribution of interacting single-domain particles. Choosing reasonable values for the saturation magnetization M_s, the anisotropy field H_a, and the mean-field interactions of the CLC model, we were able to reproduce the main features of the hysteresis curves for the x=0.02 and 0.04 samples. For higher x values, X-ray diffraction Rietveld analysis revealed the presence of other “impurity” phases, among them cubic Zr₆(Co,Fe)₂₃, rhombohedral (SmZr)₅(CoFeCu)₁₉ and rhombohedral (SmZr)₂(CoFeCu)₇.     

Crystal growth and characterisation of new organic nonlinear optical materials: 6-cyano and 6-nitro-2,2-dimethyl-3,4-epoxychroman

Two chiral organic nonlinear optical materials, (3S,4S)-(−)-6-cyano-2,2-dimethyl-3,4-epoxychroman (1) and (3R,4R)-(+)-6-nitro-2,2-dimethyl-3,4-epoxychroman (2), have been grown into single crystals of cm³-size. Although both compounds crystallise in the orthorhombic P2₁2₁2₁ space group, they are not isomorphous and their crystal packings are quite different. Angle tuned type II phase-matched second harmonic generation between 0.8 and 1.064 μm has been evidenced, with effective nonlinear coefficients d_eff of 1 and 5 pm/V at 0.96 μm for 1 and 2, respectively. These values are in agreement with those estimated in the oriented gas model approximation using EFISH first order hyperpolarisability values (β₀=2.6 and 4.0×10⁻³⁰ esu for 1 and 2, respectively).     

A Compensation Temperature Study of Bond-Diluted Mixed Ising Ferrimagnetic Spin System with Different Transverse Fields

The magnetic properties of bond-diluted nearest-neighbor interaction mixed spin-1/2 and spin-1 Ising ferrimagnetic spin system with different transverse fields are investigated within the framework of the finite cluster approximation (FCA). Particular emphasis is given to the square lattice with coordination number 2 = 4 for which magnetizations are obtained. The interactions Jij are assumed to be independent random variable with distribution P(J_ij) = pδ(J_ij-J) + (1-p)δ(J_ij), where J < 0. If bond concentration p varies in the certain ranges, we find that the compensation temperature is obtained for the values of the different transverse fields Ω_1/2 and Ω₁ in a restricted region. We obtain the values of the critical different transverse fields and critical bond concentration in this paper.     

Scaling Behavior of an Aggregation-Migration Model

We study the kinetic behavior of a two-species aggregation-migration model in which an irreversible aggregation occurs between any two clusters of the same species and a reversible migration occurs simultaneously between two different species. For a simple model with constant aggregation rates and with the migration rates K_A(i;j)=K'_A(i;j) ∝ij^v₁ and K_B(i;j)=K'_B(i;j) ∝ij^v₂, we find that the evolution behavior of the system depends crucially on the values of the indexes v₁ and v₂. The aggregate size distribution of either species obeys a conventional scaling law for most cases. Moreover, we also generalize the two-species system to the multi-species case and analyze its kinetic behavior under the symmetrical conditions.     

Computer simulation of a carbon-deposition plasma in CH4

A transport and reaction model of a low-pressure, high-frequency (13.56 MHz) CH₄ plasma used for diamondlike carbon (a-C:H) deposition was developed. The model includes reactions among four molecular species (CH₄, C₂ H₆, C₂H₄, and H₂), five radicals and atom (CH₃, CH₂, CH, C₂H₅, and H), and four ions (CH₄⁺ , CH₃⁺, CH₅⁺, and C ₂H₅⁺). It also accounts for the influence of the sticking coefficient of species at the walls. Calculated values of the dissociation degree for several flow rates are in good agreement with experimental measurements made by quadrupole mass spectroscopy. A simple surface-model based on the hydrogen coverage of surface and ion flux and energy at the substrate surface was established. This model permitted the calculation of the deposition rate on the powered electrode as a function of the power applied to this electrode. Good agreement between experimental and calculated growth rates was obtained when CH₃, C₂H₅, and CH₂ were assumed to participate in film formation, and when hydrogen removal by ion bombardment with variable energy as a function of the power was included in the model     

霍尔推进器壁面材料二次电子发射及鞘层特性

霍尔推进器放电通道等离子体与壁面相互作用形成鞘层,不同壁面材料的二次电子发射对推进器鞘层特性具有重要影响,本文针对推进器壁面鞘层区域建立二维物理模型,研究了氮化硼(BN)、碳化硅(SiC)和三氧化二铝(Al_2O_3)三种不同壁面材料的二次电子发射特性,在改进SiC材料二次电子发射模型的基础上,采用粒子模拟方法,讨论了壁面二次电子发射系数与电子温度和磁场强度的关系,研究了三种材料(BN,SiC和Al_2O_3)的鞘层特性,结果表明:修正的二次电子发射模型拟合曲线与实验曲线几乎一致;在相同电子温度下,三种材料(BN,SiC和Al_2O_3)的二次电子发射系数和壁面电子数密度依次增大,而鞘层电场和鞘层电势降依次减小,BN材料具有合适的二次电子发生射系数,使得霍尔推进器能在低电流下稳态工作。     

非金属二元氢化物分子振动固有频率与pKa常数的定量关系

提出了非金属二元氢化物分子振动固有频率的计算原理与方法.将基频和总频作为结构信息指数用于非金属二元氢化物的分子结构与pK_a常数的定量关系研究,结果表明,其相关系数大于0.995,得到的回归方程用于pK_a的计算,计算值与实验值比较,平均绝对误差小于1.82.     

氟哌酸1HNMR的测定及过渡金属离子对其影响

氟哌酸^*[即1-乙基-6-氟-4-氧-7-(1-哌嗪)-3-(1,4-二氢化喹啉甲酸]是一种广谱、安全、有效、可供口服的抗感染药。我们测定了它的¹H自旋-晶格弛豫时间T₁及其在Cr³⁺、Mn²⁺、和Fe³⁺等过渡金属离子存在下的T₁值。实验结果表明,在加入过渡金属离子前后,氟哌酸不同位¹H的T₁值发生了一定的变化。据此可揭示过渡金属离子和氟哌酸形成配合物的配位点,从而可确定所形成配合物的结构。     

C掺杂金红石相TiO2的电子结构和光学性质的第一性原理研究

运用第一性原理的局域密度近似+U(0 ≤U≤9 eV)方法研究了本征金红石相TiO₂在不同U值(对Ti-3d电子)下的禁带宽度、晶体结构以及不同比例C元素掺杂的金红石相TiO₂的电子结构和光学性质, 研究表明, TiO₂的禁带宽度和晶格常数随着U值的增加而增大. 综合考虑取U=3 eV并对其计算结果进行修正. 对于掺杂体系, 发现C 元素的掺杂在金红石相TiO₂中引入杂质能级, 杂质能级主要由O-2p轨道和C-2p轨道耦合形成, 杂质能级的引入可以增加TiO₂对可见光的响应, 从而使TiO₂的吸收范围增大. C原子掺杂最佳比例为8.3%, 此时光学吸收边的红移程度最明显, 可增大光吸收效率, 从而提高了TiO₂光催化效率.     

Characterization of RuO2 thin films by Raman spectroscopy

Raman scattering has been used as a technique for the characterization of RuO₂ thin films deposited on different substrates by the metal-organic chemical vapor deposition method and reactive sputtering under various conditions. Red shift and broadening of the linewidth of the Raman peaks are analyzed by the spatial correlation model. The intrinsic linewidth for the RuO₂ films deposited at high and low temperatures has to be adjusted to different values to achieve a good fit for the features. The lineshape and position of the Raman features vary for films deposited on different substrates under the same condition. These differences indicate the existence of stress induced by lattice mismatch and the differential thermal expansion coefficients between RuO₂ and the substrates. After annealing at 650°C in an oxygen atmosphere for 3 h, the linewidth decreases significantly for the RuO₂ thin films deposited at lower temperatures. The results show the improvement of the crystallinity of the films during the annealing process.     

基于近红外光谱检测技术的水泥生料成分含量检测研究

近红外光谱检测技术已经成功应用于水泥生料成分的快速检测,但我国水泥企业在生产水泥生料时所用原材料品种不一,使用不同的原材料进行生产时对近红外光谱建模带来一定影响.为了研究不同原料生产的水泥生料近红外光谱建模差异,对不同地区水泥生产线所生产的水泥生料进行建模研究.选取两个不同地区水泥生产线的水泥生料样本各95份和82份,...     

Dynamic behaviors of water contained in calcium-silicate-hydrate gel at different temperatures studied by quasi-elastic neutron scattering spectroscopy

The dynamic behaviors of water contained in calcium-silicate-hydrate(C-S-H) gel with different water content values from 10%to 30%(by weight),are studied by using an empirical diffusion model(EDM) to analyze the experimental data of quasi-elastic neutron scattering(QENS) spectra at measured temperatures ranging from 230 K to 280 K.In the study,the experimental QENS spectra with the whole Q-range are considered.Several important parameters including the bound/immobile water elastic coefficient A,the bound water index BWI,the Lorentzian with a half-width at half-maximum(HWHM) Γ_1(Q) and Γ_2(Q),the self-diffusion coefficients D_(t1) and D_(t2) of water molecules,the average residence times τ_(01)and τ_(02),and the proton mean squared displacement(MSD)(u~2) are obtained.The results show that the QENS spectra can be fitted very well not only for small Q(≤1 A~1) but also for large Q.The bound/immobile water fraction in a C-S-H gel sample can be shown by the fitted BWI.The distinction between bound/immobile and mobile water,which includes confined water and ultra-confined water,can be seen by the fitted MSD.All the MSD tend to be the smallest value below 0.25 A~2(the MSD of bound/immobile water) as the Q increases to 1.9 A~1 no matter what the temperature and water content are.Furthermore,by the abrupt changes of the fitted values of D_(t1),τ_(01),and Γ_1(Q),a crossover temperature at 250 K,namely the liquid-to-crystal-like transition temperature,can be identified for confined water in large gel pores(LGPs) and/or small gel pores(SGPs) contained in the C-S-H gel sample with 30% water content.     

外电场下二氧化硫的分子结构及其特性

以6-311++g(3d, p)为基组, 采用B3P86方法研究了不同外电场(-0.04-0.04 a.u.)对SO₂分子基态的几何参数、电荷分布、能量、电偶极距、最高占据轨道(HOMO)能级、最低占据轨道(LUMO)能级及能隙的影响, 在优化构型的基础上, 采用含时密度泛函(TD-B3P86)方法研究了SO₂分子在外电场作用下前9个激发态的激发能、跃迁波长和振子强度. 研究表明: SO₂的几何参数与电场强度大小及方向均有明显的依赖关系. 电场由-0.04 a.u. 变化至0.04 a.u.时, 体系的总能量先增加后减小; 偶极矩先减小后增加; HOMO能级一直减小; LUMO能级先增加后减小; 能隙先增加后减小. 激发态的激发能、跃迁波长和振子强度与电场关联均较为复杂, 说明SO₂的激发特性易受外电场影响.