Atomic resolution of bond descriptors in the two-orbital model

The probability-resolution scheme for partitioning the molecular bond-multiplicities into atomic contributions, suggested by the ‘partial’ atomic channels of the Communication Theory of the chemical bond, is applied to the simplest two-orbital model of a diatomic molecule. It offers a unique perspective upon a degree of the atom involvement in the covalent and ionic interactions with its molecular environment. The row channels generate the atomic contributions to the molecular bond-multiplicity and its covalent/ionic composition, while the atomic column channels give rise to the valence indices of bonded atoms, which reflect their promoted states in a molecule. Plots of the entropy/information bond indicators of atomic partial communication channels are generated over the whole range of the probability of finding an electron on the specified atom, 0?≤?P?≤?1, which measures a degree of polarization of the bonding molecular orbital (MO). They are compared with the MO predictions obtained from the same probability-division rule of the molecular bond-order measures from the MO theory. The atomic bond indices from the communication-theory approach are shown to agree semi-quantitatively with predictions from the MO theory.     

甲醇荧光光谱的量子分析

通过量子近似计算研究了甲醇的荧光光谱.将甲醇分子近似看成双原子分子,甲基和羟基分别为原子实,氧原子未共享电子对看成价电子.利用数值计算的方法对双原子分子电子能级差进行估算,得到电子能级差为一个仅与分子线度相关的函数.然后把C-O键长作为分子线度代入前面得到的函数中,算出甲醇分子主跃迁能级差,并将所得结果与实验值进行对比,误差仅为2.2%,理论计算与实验结果吻合.     

利用电子结构数据拟合H2分子的电子壳模型势函数参数

电子壳模型势函数在离子晶体的原子级计算机模拟中有广泛应用,其势参数主要通过拟合晶体的实验数据或电子结构数据得到.提出了通过拟合双原子分子的量子化学从头计算电子结构数据来获得该势函数的方法,并由H2分子的电子结构数据建立了H原子间的电子壳模型势函数.此外,还应用该势函数对H+2分子离子进行了计算.该势函数拟合方案更适合于共价键型的分子.     

重离子核反应中丰中子余核产额的标度规律

在重离子碰撞（HICs）的实验数据和动力学模拟的反应中发现了丰中子余核产额的标度现象。在这种标度现象中,两个同位旋不同的炮弹碎裂反应产生的余核中,不同中子丰度差的余核的信息熵不确定度的差具有一致的分布。利用反对称化分子动力学模型（AMD）模拟并联合退激发模型（GEMINI）模拟了140 AMeV 58,64Ni+9Be碰撞体系中余核的产额,并展示了实验测量的余核已经理论模拟得到的余核的标度现象。由于信息熵方法对反应系统是否处于平衡状态没有要求,不仅可以用于处于平衡态系统的核物质研究,也可以用于动力学变化过程中的核物质性质研究。信息熵方法将为HICs中的核物质演化研究提供新的理论分析方法。A scaling phenomena has been discovered for fragments produced in heavy-ion collisions both in the measured experiments and in the simulated reactions by transport model. In this scaling phenomena, the information entropy uncertainty difference between isobars with different neutron-excess has a uniform distribution between two reactions. The simulated reactions of 140 AMeV 58,64Ni+9Be by using the asymmetric molecular dynamics(AMD) model plus the sequential decay code GEMINI are analyzed to show the scaling phenomena of fragments. Since the application of information entropy theory does not require the system to be in equilibrium, it can be used both in the analysis of transport model and thermodynamics models. The advantage of the information entropy theory provides a new method to study the dynamical evolution of nuclear matter inheavy-ion collisions.     

利用电子结构数据拟合H2分子的电子壳模型势函数参数

电子壳模型势函数在离子晶体的原子级计算机模拟中有广泛应用,其势参数主要通过拟合晶体的实验数据或电子结构数据得到.提出了通过拟合双原子分子的量子化学从头计算电子结构数据来获得该势函数的方法,并由H₂分子的电子结构数据建立了H原子间的电子壳模型势函数.此外,还应用该势函数对H⁺₂分子离子进行了计算.该势函数拟合方案更适合于共价键型的分子. 关键词： 电子壳模型势 参数拟合 共价键 2分子')" href="#">H₂分子     

Manipulation of individual hyperfine states in cold trapped molecular ions and application to HD+ frequency metrology

Advanced techniques for manipulation of internal states, standard in atomic physics, are demonstrated for a charged molecular species for the first time. We address individual hyperfine states of rovibrational levels of a diatomic ion by optical excitation of individual hyperfine transitions, and achieve controlled transfer of population into a selected hyperfine state. We use molecular hydrogen ions (HD+) as a model system and employ a novel frequency-comb-based, continuous-wave 5 μm laser spectrometer. The achieved spectral resolution is the highest obtained so far in the optical domain on a molecular ion species. As a consequence, we are also able to perform the most precise test yet of the ab initio theory of a molecule.     

Quantitative energy level correlations for linear,bent and internally rotating triatomic molecules

This paper is concerned with the study of the quantitative correlation of the rotation-bending energy levels of a linear or bent triatomic molecule with the energy levels of the molecule when there is free internal rotation of a diatomic fragment [as in, for example, Ar(HCl)]. The LiNC and KCN molecules are used as model systems. A correlation parameter γ_r is introduced to quantify the position a molecule occupies in these correlation diagrams; this parameter has the value +1 for an ideal bent molecule, ?1 for an ideal linear molecule, and ?3 for an ideal free internal rotor triatomic molecule. The rotation-bending energy levels of the HCN-HNC isomerization system, and of the double minimum HO₂ system, are also studied.     

Classical dynamics of laser-driven D₃⁺

A classical model of the triatomic D?? molecule subjected to an intense, few-cycle laser pulse is introduced. The model is capable of describing the laser-induced correlated motion of both electrons and nuclei in three dimensions, and allows us to follow the motion of the two electrons and three deuterons from the initial field-free state, during the pulse, and until the bond breaking into the final fragments. By averaging over many trajectories, we calculate the relative yields of the ionization and dissociation channels, as well as the kinetic energy release (KER) from the fragment ions. A comparison with recent experimental KER spectra shows good qualitative agreement. In addition, we find a pathway in which an emitted electron recombines into a high-lying Rydberg state, resulting in D + D? + D? fragments with the same KER as in the D? + D? + D? channel.     

Angular distributions of the fragments from coulomb explosions of diatomic molecules in intense laser fields

The angular distributions of the fragments from a Coulomb explosion of a diatomic heteronuclear molecule during multielectron dissociative ionization in a superintense field are considered in terms of classical mechanics. The patterns of angular distributions of the Coulomb explosion fragments are shown to differ in different ranges of laser pulse parameters. In particular, there are two distinct modes of fragment separation: separation in a Coulomb field and separation in the field of an effective “fragment + field” potential. The effective potential includes both the force of Coulomb repulsion between the fragments and the period-averaged force exerted on the system by the field; it can be determined by using the Kramers-Henneberger method. The limits of applicability of the Kramers-Henneberger method to the problem in question are discussed. These limits specify the range of field parameters in which the fragments fly apart in a direction perpendicular to the field for the initially arbitrary orientation of the molecular axis relative to the field.     

普适性双原子分子解析势能函数的研究

提出了一种构造解析势能函数的新方法,由此得到了一种既适用于中性双原子分子又适用于带电双原子分子离子的解析势能函数。本文用八种基本类型的双原子分子——同核中性基态双原子分子Na₂-X1Σ+_g,同核中性激发态双原子分子C₂-A1Π_u,同核带电基态双原子分子离子He+₂-X2Σ+_u,同核带电激发态双原子分子离子N+₂-B2Σ+_u,异核中性基态双原子分子NaLi-X1Σ+_g,异核中性激发态双原子分子BH-B1Σ+,异核带电基态双原子分子离子(BC)--X3Π,异核带电激发态双原子分子离子(CS)+-A2Π等共21个算例对势能函数进行了验证并与RKR (Rydberg-Klein-Rees)实验数据进行了比较,计算结果与RKR数据符合很好。     

The Special Features of the Electronic Structure of Imperfect and Interacting Low-Dimensional Nanoparticles

A new method for constructing analytic exactly solvable models of the electronic structure of imperfect and interacting low-dimensional nanoparticles is suggested. The method uses the approach based on multiple scattering theory. It allows characteristic equations to be written specifying the contributions of exchange interactions between separate atoms, nanoparticle fragments, or interacting nanoparticles. The possibilities of the method are demonstrated for the example of one-dimensional and quasi-one-dimensional finite regular structures with monovacancies and isolated attached atoms and diatomic molecules. We also consider regular structures composed of two interacting low-dimensional nanoparticles. The general characteristic of the electronic spectra of the systems under consideration is qualitative changes in the system of energy levels and electron density distributions as a result of the formation of defects or new bonds between subsystems. These changes can substantially influence all the physical and chemical properties of nanoparticles.     

分子和金表面相互作用的第一性原理研究

从第一性原理出发利用密度泛函理论研究了 4 ,4′ 二巯基联苯分子和金表面的相互作用 ,并利用了前线轨道理论和微扰理论定量地确定了该相互作用能常数. By using density functional theory, we have investigated the interaction between a thiol-phenyl molecule (4-4′-dimercaptodibenzene) and a gold surface. The frontier orbit theory and the perturbation theory are also employed to determine quantitatively the constant of interaction energy. The results show that the bonding between the sulfur atom and the gold atoms corresponds mainly to the covalent bond and some molecular orbits are extended over the molecule and gold cluster which certainly give channels...     

非对称双原子分子在输运扩散中的取向效应

本文建立了同时具有化学势梯度和温度梯度的非平衡系统,研究非对称双原子分子的输运扩散行为.研究发现,双原子分子在非平衡输运中具有取向效应.浓度梯度与温度梯度使双原子分子在输运中产生的大小原子取向的方向刚好相反,沿着梯度的正方向,前者使小原子在前,后者使大原子在前.通过最小熵产生原理,解释了取向的物理机制.研究结果对于深刻理解非平衡条件下物质的输运与其形态的关系具有理论意义.     

基于密度泛函理论的外电场下C_3F_8微观特性的研究

全氟丙烷(C_3F_8)作为一种拥有较低温室效应的SF_6替代气体,被国内外学者广泛研究.为了从分子层面上揭示全氟丙烷在外电场作用下微观特性的变化情况,采用密度泛函理论中的M06-2X方法,在6-31G(d)基组水平上优化得到了C_3F_8的基态稳定构型.分析了不同外电场(0-0.020 a.u.)对C_3F_8分子的结构、Highest Occupied Molecular(HOMO)、Lowest Unoccupied Molecular(LUMO)、能隙、键级的影响,并研究了全氟丙烷分子的激发态能、波长、振子强度.结果表明,在所加电场范围内,随着电场强度的增大,C_3F_8分子最高占据轨道能级逐渐增大,最低空轨道能级逐渐减小,能隙E_G逐渐减小, C_3F_8分子的化学活性增强;C_3F_8分子中的C-C键的Mayer Bond Order (MBO)值随电场强度的增大均出现增大的情况,分子的稳定性降低;C_3F_8分子激发态的激发能总体上呈现出减小的趋势,激发态的波长总体上则呈现出增大的趋势,表明在外电场的作用下,全氟丙烷分子变得越来越容易激发.     

Ni2分子结构和分子轨道密度(DMO)的成键贡献

用密度泛函(B3P86/6-311g*)方法研究了Ni2分子结构和势能函数.结果表明基态Ni2为5Πg,平衡间距为Re=0.223 196 nm,离解能为1.851 16 eV.定义了分子轨道密度(DMO, density of molecular orbital)并研究了镍双原子分子的s, p, d, f的DMO对成键的贡献,为进一步研究金属的态密度提供了有益的参考价值.     

Coarse-graining stiff bonds

The method of constraints in molecular dynamics is useful because it avoids the resolution of high frequency motions with very small time steps. However, the price to pay is that both the dynamics and the statistics of a constrained system differ from those of the unconstrained one. Instead of using constraints, we propose to dispose of high frequency motions by a coarse-graining procedure in which fast variables are eliminated. These fast variables are thus modeled as friction and thermal fluctuations. We illustrate the methodology with a simple model case, a diatomic molecule in a monoatomic solvent, in which the bond between the atoms of a diatomic molecule is stiff. Although the example is very simple and does not display the interesting effects of “wrong” statistics of the constrained system (i.e. the well-known issue connected to the Fixman potential), it is well suited to give the proof of concept of the whole procedure.     

Christopher Longuet-Higgins, 1923 to 2004

The structure, harmonic vibrational frequencies, dissociation energies with respect to possible fragmentation pathways, dipole moment, natural bond orbital (NBO) partial atomic charges and time-dependent density functional theory (TD-DFT) excitation energies for the novel molecule periodane, FBeCNLiOB, and three structural analogues were computed using density functional theory (DFT). Two isoelectronic analogues (FBeCNLiNC and FBeBOLiOB) result from the replacement in periodane of the BO fragment with the CN fragment and vice versa, while the third, called hydroperiodane, is formed by replacing the F atom of periodane with a H atom. These three species are predicted to have a stable structural motif based on that of the theoretically predicted planar global minimum of the periodane molecule.