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Theoretical study of [4 + 2] cycloadditions of some 6- and 5-member ring aromatic compounds on the Si(001)-2 × 1 surface: correlation between binding energy and resonance energy Si(001)-2 × 1表面上一些6元和5元环芳香族化合物[4 + 2]环加成的理论研究:结合能和共振能的关系
Pub Date : 2001-06-21 DOI: 10.1039/B104187H
Xin Lu, M. Lin, Xin Xu, Nanqin Wang, Qianer Zhang
By means of first-principles density functional cluster model calculations, we demonstrate that the binding energies of the [4 + 2] cycloaddition products of the 6- and 5-member ring aromatic compounds on the Si(001) surface depend strongly on their resonance energies.
通过第一性原理密度泛函簇模型计算,我们证明了6元和5元环芳香族化合物在Si(001)表面的[4 + 2]环加成产物的结合能强烈依赖于它们的共振能。
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引用次数: 5
Quantum computing and nuclear magnetic resonance 量子计算和核磁共振
Pub Date : 2001-06-12 DOI: 10.1039/b103231n
J. A. Jones
Quantum information processing is the use of inherently quantum mechanical phenomena to perform information processing tasks that cannot be achieved using conventional classical information technologies. One famous example is quantum computing, which would permit calculations to be performed that are beyond the reach of any conceivable conventional computer. Initially it appeared that actually building a quantum computer would be extremely difficult, but in the last few years there has been an explosion of interest in the use of techniques adapted from conventional liquid state nuclear magnetic resonance (NMR) experiments to build small quantum computers. After a brief introduction to quantum computing I will review the current state of the art, describe some of the topics of current interest, and assess the long term contribution of NMR studies to the eventual implementation of practical quantum computers capable of solving real computational problems.
量子信息处理是利用固有的量子力学现象来完成传统经典信息技术无法实现的信息处理任务。一个著名的例子是量子计算,它将允许执行任何传统计算机无法想象的计算。最初,建造一台量子计算机似乎是非常困难的,但在过去的几年里,人们对使用传统的液态核磁共振(NMR)实验技术来建造小型量子计算机的兴趣激增。在简要介绍量子计算之后,我将回顾当前的艺术状态,描述当前感兴趣的一些主题,并评估核磁共振研究对最终实现能够解决实际计算问题的实用量子计算机的长期贡献。
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引用次数: 16
Energy transfer efficiency distributions in polymers in solution during folding and unfolding 聚合物在折叠和展开过程中的能量传递效率分布
Pub Date : 2001-05-07 DOI: 10.1039/B200595F
G. Srinivas, B. Bagchi
Distribution of fluorescence resonance energy transfer (FRET) efficiency between the two ends of a Lennard-Jones polymer chain both at equilibrium and during folding and unfolding has been calculated, for the first time, by Brownian dynamics simulations. The distribution of FRET efficiency becomes bimodal during folding of the extended state subsequent to a temperature quench, with the width of the distribution for the extended state broader than that for the folded state. The reverse process of unfolding subsequent to a upward temperature jump shows different characteristics. The distributions show significant viscosity dependence which can be tested against experiments.
通过布朗动力学模拟,首次计算了伦纳德-琼斯聚合物链两端在平衡状态和折叠展开过程中的荧光共振能量转移(FRET)效率分布。在温度淬火后的扩展态折叠过程中,FRET效率的分布呈双峰分布,且扩展态的分布宽度大于折叠态的分布宽度。温度上升后的反向展开过程表现出不同的特征。分布表现出明显的粘度依赖性,这可以通过实验来验证。
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引用次数: 1
MIDIX basis set for the lithium atom: Accurate geometries and atomic partial charges for lithium compounds with minimal computational cost 锂原子的MIDIX基础设置:精确的几何形状和锂化合物的原子部分电荷与最小的计算成本
Pub Date : 2001-01-01 DOI: 10.1039/B105076C
Jason D. Thompson, P. Winget, D. Truhlar
We present a MIDIX basis set for Li that accurately predicts geometries, charge distributions, and partial atomic charges for a test set of compounds at a reasonable cost. MIDIX basis sets, which are also called MIDI!, are heteroatom-polarized split-valence basis sets in which the polarization functions are optimized in order to predict realistic molecular geometries and atomic partial charges. The MIDIX basis set uses the core, inner valence, and outer valence basis functions of the MIDI basis set plus an additional Gaussian basis function. We optimized the p exponent to obtain realistic predictions of geometry, density dipole moments, and Lowdin dipole moments at the Hartree–Fock and hybrid density functional levels of theory, using the mPW1PW91 hybrid density functional for the latter. The MIDIX basis set predicts Hartree–Fock geometries and Hartree–Fock and hybrid density functional Lowdin dipole moments more accurately than either the 3-21G(d) or 6-31G(d) basis set for most of the compounds in our training set. It also predicts more accurate Hartree–Fock and hybrid density functional density dipole moments than the 3-21G(d) basis set. The present results show that the basis set is expected to be very useful for calculating geometries and electrostatic properties of lithium compounds containing H, C, N, O, F, Si, P, S, Cl, Br, and I, especially organolithium and lithium–sulfur compounds.
我们为Li提供了一个MIDIX基础集,可以以合理的成本准确地预测化合物测试集的几何形状、电荷分布和部分原子电荷。middix基础集,也叫MIDI!,是杂原子极化分裂价基集,其中极化函数经过优化,以预测实际的分子几何形状和原子部分电荷。MIDIX基集使用MIDI基集的核心、内部价和外部价基函数加上一个额外的高斯基函数。我们优化了p指数,在Hartree-Fock和混合密度泛函的理论水平上获得了几何、密度偶极矩和Lowdin偶极矩的现实预测,使用mPW1PW91混合密度泛函对后者进行了预测。对于我们训练集中的大多数化合物,MIDIX基集比3-21G(d)或6-31G(d)基集更准确地预测Hartree-Fock几何形状以及Hartree-Fock和混合密度函数Lowdin偶极矩。与3-21G(d)基集相比,它还能更准确地预测Hartree-Fock和杂化密度泛函数密度偶极矩。本研究结果表明,该基集有望用于计算含H、C、N、O、F、Si、P、S、Cl、Br和I的锂化合物的几何形状和静电性质,特别是有机锂和锂硫化合物。
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引用次数: 11
Assignment of the near-UV absorption spectrum of C60 C60近紫外吸收光谱的确定
Pub Date : 2001-01-01 DOI: 10.1039/B109221A
A. Sassara, G. Zerza, M. Chergui
The absorption spectrum of C 60 embedded in Ne matrices in the 410–360 nm region is revisited. A complete assignment of the absorption lines therein is proposed in terms of transitions to the ungerade states 1 1 G u , 1 1 T 1u and 2 1 T 1u states, with progressions of Jahn–Teller h g modes and of the totally symmetric a g modes. We also identify a new progression at λ= 375 nm, which we attribute to the transition to a state of G u character and its h g and g g Jahn–Teller modes. Its pure electronic origin is at ∼26700 cm –1 .
重新研究了c60在410 ~ 360nm范围内的吸收光谱。利用Jahn-Teller h G模和完全对称的A G模的级数,提出了其中的吸收谱线的完全赋值,即向非梯度态11gu、11t1u和21t1u态的跃迁。我们还在λ= 375 nm处发现了一个新的级数,我们将其归因于向G特征态及其h G和G G Jahn-Teller模式的过渡。它的纯电子源在~ 26700 cm -1。
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引用次数: 1
The self-reaction of hydroperoxyl radicals: ab initio characterization of dimer structures and reaction mechanisms 羟基自由基的自反应:二聚体结构和反应机理的从头表征
Pub Date : 2001-01-01 DOI: 10.1039/B107602G
R. Zhu, M. Lin
The global potential energy surfaces of singlet and triplet H 2 O 4 systems have been searched at the B3LYP/6-311G(d, p) level of theory; their relative energies have been calculated at the G2M(CC5)// B3LYP/6-311G(d, p) level. The results show that the most stable intermediate out of the 11 open-chain and cyclic dimers of HO 2 is the singlet HO 4 H chain-structure with C 1 symmetry which lies 19.1 kcal mol –1 below the reactants. The transition states for the production of H 2 O 2  + O 2 (singlet and triplet), H 2 O + O 3 and H 2  + 2O 2 have been calculated at the same level of theory. The results show that the most favored product channel, producing H 2 O 2  +  3 O 2 , occurs by the formation of a triplet six-member-ring intermediate through head-to-tail association with a dual hydrogen-bonding energy of 9.5 kcal mol –1 . The intermediate fragments to give H 2 O 2  +  3 O 2 via a transition state, which lies below the reactants by about 0.5 kcal mol –1 . There are four channels over the singlet surface which can produce 1 O 2 ; all the transition states associated with these channels lie above the reactants by 2.8–5.6 kcal mol –1 at the G2M level. Similarly, the O 3 and H 2 formation channels also occur over the singlet surface with high energy barriers, 5.2 and 74.2 kcal mol –1 , respectively; their formation is kinetically unimportant.
在B3LYP/6-311G(d, p)理论水平上研究了单重态和三重态h2o体系的总势能面;在G2M(CC5)// B3LYP/6-311G(d, p)能级计算了它们的相对能量。结果表明,在11种ho2开链环二聚体中,最稳定的中间体是c1对称的单线态ho4h链结构,位于反应物下方19.1 kcal mol -1。在同一理论水平上计算了生成h2o2 + o2(单重态和三重态)、h2o + o2和h2o2 + 2O的过渡态。结果表明,在双氢键能为9.5 kcal mol -1的条件下,通过首尾结合形成三重态六元环中间体,生成h2o2 + 3o2,是最有利的产物通道。中间片段通过过渡态生成h2o2 + 3o2,该过渡态位于反应物下方约0.5 kcal mol -1。单线态表面上有四个通道,可以产生1 O 2;在G2M水平上,与这些通道相关的所有过渡态都比反应物高2.8-5.6 kcal mol -1。同样,o3和h2的形成通道也出现在单线态表面,具有高能量垒,分别为5.2和74.2 kcal mol -1;它们的形成在动力学上不重要。
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引用次数: 23
Application of generalized two-dimensional correlation theory to gel permeation chromatographic analysis 广义二维相关理论在凝胶渗透色谱分析中的应用
Pub Date : 2001-01-01 DOI: 10.1039/B103810A
K. Izawa, T. Ogasawara, H. Masuda, H. Okabayashi, I. Noda
This report demonstrates the promising potential for the application of generalized two-dimensional correlation analysis to time dependent GPC elution profiles, in analysis of complex dynamic variations in the sol–gel polymerization process.
该报告展示了将广义二维相关分析应用于随时间变化的GPC洗脱剖面,分析溶胶-凝胶聚合过程中复杂的动态变化的潜力。
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引用次数: 5
The visualisation of chemical processes for electronic publishing and presentations 用于电子出版和演示的化学过程的可视化
Pub Date : 2001-01-01 DOI: 10.1039/B103982M
P. May
Over the past ten years, there has been a huge increase in desktop computer power, leading to explosive growth of the internet and the now widespread use of electronic media for publication and presentation of scientific documents. These new innovations have provided a challenge, as well as great opportunity, for a visual subject such as chemistry to present itself in a much more appealing way than has previously been possible. This article attempts to demonstrate how easy it is to create visually impressive chemical images and animations, as well as interactive structures and spectra, for use in lectures, on-line courses, electronic journal articles, web pages, etc. This is intended to be an introductory article to show potential authors how easy it is to add valuable extra content to their scientific documents, and at the same time make them more visually attractive. Topics covered include: animated gif images, creating and displaying interactive 3D molecular structures, creating 3D structure animations, creating and displaying molecular orbitals, and interactive spectra.
在过去的十年里,台式计算机的能力有了巨大的增长,导致了互联网的爆炸式增长,以及现在广泛使用电子媒体来出版和展示科学文献。这些新的创新为化学这样的视觉学科提供了挑战,也提供了巨大的机会,使其以比以前更有吸引力的方式呈现出来。本文试图演示创建视觉上令人印象深刻的化学图像和动画,以及交互式结构和光谱,用于讲座,在线课程,电子期刊文章,网页等是多么容易。这是一篇介绍性的文章,旨在向潜在的作者展示在他们的科学文献中添加有价值的额外内容是多么容易,同时使它们在视觉上更具吸引力。主题包括:动画gif图像,创建和显示交互式3D分子结构,创建3D结构动画,创建和显示分子轨道,以及交互光谱。
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引用次数: 0
Rotational excitation from a molecular mirror: NO scattering from Ru(0001)-(1 × 1)H 分子镜的旋转激发:Ru(0001)-(1 × 1)H的NO散射
Pub Date : 2001-01-01 DOI: 10.1039/B104823F
B. Berenbak, B. Riedmüller, C. Rettner, D. Auerbach, S. Stolte, A. Kleyn
The rotational state distributions of NO molecules scattered off the (1 × 1)H-covered Ru(0001) surface have been investigated by resonance enhanced multi-photon ionisation (REMPI). Angular and energy distributions reported earlier for this scattering channel, show an angular spread of only ≃8° (θ i  = 60°, E i  = 2.1 eV), combined with small translational energy loss in the collision (E f /E i  = 0.91). These observations suggest scattering from a very weakly corrugated surface, a ‘molecular mirror’, and a high probability to yield cold rotational distributions. The present experiments, however, reveal substantial rotational excitation, accompanied by rotational rainbows for higher quantum numbers (J > 20). The rotational temperatures increase from  = 450 K at an incidence energy E i  = 0.32 eV, to  = 950 K at E i  = 1.50 eV. The kinetic to rotational energy transfer efficacy, appears to be slightly higher than for NO scattering of the fairly inert Ag(111) surface. This system has much wider angular spread and larger translational energy losses. Assuming parallel momentum conservation in the collision the observed rotational excitation would lead to an angular spread that is considerably smaller than that observed for an incoming angle of θ i  = 15°.
用共振增强多光子电离(REMPI)研究了从(1 × 1) h覆盖的Ru(0001)表面散射的NO分子的旋转态分布。该散射通道的角向和能量分布表明,该通道的角向扩散仅为≃8°(θ i = 60°,E i = 2.1 eV),且碰撞过程中的平动能量损失较小(E f /E i = 0.91)。这些观察结果表明,散射来自一个非常弱的波纹表面,一个“分子镜子”,并且很有可能产生冷旋转分布。然而,目前的实验揭示了大量的旋转激发,并伴随着更高量子数(J > 20)的旋转彩虹。旋转温度从入射能量E i = 0.32 eV时的= 450 K增加到E i = 1.50 eV时的= 950 K。相对于惰性Ag(111)表面的NO散射,其动能到转动的能量传递效率略高。该系统具有更宽的角展和更大的平动能量损失。假设在碰撞中平行动量守恒,观察到的旋转激励将导致的角扩展比θ i = 15°时观察到的角扩展要小得多。
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引用次数: 1
Simple suppressing method of thermal runaway in microwave heating of zeolite and its application 沸石微波加热中热失控的简易抑制方法及其应用
Pub Date : 2001-01-01 DOI: 10.1039/B009067K
Ohgushi Tatsuo, Wakana Akiko
4A, 13X and Na-mordenite (Na-M) reached higher temperatures by the microwave radiation of 5–10 min in the 500 W radiation power and were completely damaged. When 5A was added to 4A, 13X or Na-M with a suitable ratio, the heating temperature of the mixture was suppressed to a desirable range and the mixture reached the dehydration degree of >85% in 15–20 min. The mixtures irradiated in desirable conditions only slightly decreased their absorption ability for water (by <5% per radiation treatment). The proposed method could quickly and simply reactivate the zeolites up to a high level with a domestic type microwave oven.
4A、13X和na -丝光沸石(Na-M)在500 W的辐射功率下,经过5 ~ 10 min的微波辐射,达到较高的温度,并被完全破坏。当5A以合适的比例加入4A、13X或Na-M时,混合物的加热温度被抑制在理想的范围内,混合物在15-20 min内达到脱水程度>85%。在理想条件下辐照的混合物仅略微降低其对水的吸收能力(每次辐照<5%)。该方法可以在家用微波炉上快速简单地将沸石重新激活到高水平。
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引用次数: 6
期刊
PhysChemComm
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