Ground state properties and potential energy surfaces of ~(270)Hs from multidimensionally-constrained relativistic mean field model

We study the ground state properties,potential energy curves and potential energy surfaces of the superheavy nucleus 270Hs by using the multidimensionally-constrained relativistic mean-field model with the efFective interaction PC-PK1.The binding energy,size and shape as well as single particle shell structure corresponding to the ground state of this nucleus are obtained.270Hs is well deformed and exhibits deformed doubly magic feature in the single neutron and proton level schemes.One-dimensional potential energy curves and two-dimensional potential energy surfaces are calculated for 270Hs with various spatial symmetries imposed.We investigate in detail the effects of the reflection asymmetric and tri axial distortions on the fission barrier and fission path of 270Hs.When the axial symmetry is imposed,the reflection symmetric and reflection asymmetric fission barriers both show a double-hump structure and the former is highe匚However,when tri axial shapes are allowed the reflection symmetric barrier is lowered very much and then the reflection symmetric fission path becomes favorable.     

He-N_2势能表面对散射截面的影响

从总散射截面、微分散射截面和分波散射截面三方面对He-N2体系的三个势能表面进行了详细比较。计算中采用了精确度较高的密耦(Close-Coupling)近似方法(E=64meV),计算结果与MKeil等的实验结果基本相符。研究结果表明:势能球平均零点能位置、势阱深度、排斥势的强度以及势能在势阱附近的方向性都对散射截面有较大的影响,为根据散射截面准确地确定He-N2体系的相互作用势能参数提供了一种新依据。     

S2O分子高激发振动光谱及势能面的代数研究

本文利用代数方法研究了非对称弯曲三原子分子S2O分子处于C～1A′电子态的能谱及其稳定构型下的势能面,通过对30条光谱数据的拟和得到的RMS误差为2.40 cm-1.结果表明,利用此代数Hamiltonian很好的实现了能级再现,它预测了振动总量子数达到20的全部振动能级(在本文中我们只列举到v= 9),同时我们计算了分子的解离能与力常数.通过与实验值比较证明了这种方法在计算这类分子的有效性.     

Macroscopic-microscopic calculations of fission potential surface of uranium isotopes in the three quadratic surfaces parametrization

Five-dimensional (5D) fission potential energy surfaces (PES) for uranium nuclei are investigated based on the macroscopic-microscopic Lublin-Strasbourg drop model in the three-quadratic-surface parametrization, and the heights of static fission barriers are obtained. Asymmetric and symmetric fission paths are presented on the 5D PES of ²³⁶U for different nuclear shapes. The calculated barrier heights, E_A and E_B, are quite consistent with the experimental data for all even-even nuclei of uranium isotopes, from ²³⁰U to ²⁴⁴U.     

Kr-CS体系势能面及束缚态能级的理论研究

本文利用从头算方法首次计算得到Kr原子与CS分子在“冻结核”近似下的相互作用离散势能点, 并拟合得到二维势能面. 该体系在R=7.76 a0, =111.4o处存在一个近T型的全域极小值, 势能值为-178.54 cm-1, 整个势能面表现较强的各向异性. 在该势能面基础上数值求解体系的薛定谔方程, 计算得到体系J ≤ 15的束缚态能级及微波谱跃迁频率.     

The potential energy surface and chaos in 2D Hamiltonian systems

We provide a new insight into the relationship between the geometric property of the potential energy surface and chaotic behavior of 2D Hamiltonian dynamical systems, and give an indicator of chaos based on the geometric property of the potential energy surface by defining Mean Convex Index (MCI). We also discuss a model of unstable Hamiltonian in detail, and show our results in good agreement with HBLSL's (Horwitz, Ben Zion, Lewkowicz, Schiffer and Levitan) new Riemannian geometric criterion.     

Low-rank canonical-tensor decomposition of potential energy surfaces: application to grid-based diagrammatic vibrational Green's function theory

ABSTRACT

A new method is proposed for a fast evaluation of high-dimensional integrals of potential energy surfaces (PES) that arise in many areas of quantum dynamics. It decomposes a PES into a canonical low-rank tensor format, reducing its integral into a relatively short sum of products of low-dimensional integrals. The decomposition is achieved by the alternating least squares (ALS) algorithm, requiring only a small number of single-point energy evaluations. Therefore, it eradicates a force-constant evaluation as the hotspot of many quantum dynamics simulations and also possibly lifts the curse of dimensionality. This general method is applied to the anharmonic vibrational zero-point and transition energy calculations of molecules using the second-order diagrammatic vibrational many-body Green's function (XVH2) theory with a harmonic-approximation reference. In this application, high dimensional PES and Green's functions are both subjected to a low-rank decomposition. Evaluating the molecular integrals over a low-rank PES and Green's functions as sums of low-dimensional integrals using the Gauss–Hermite quadrature, this canonical-tensor-decomposition-based XVH2 (CT-XVH2) achieves an accuracy of 0.1 cm^?1 or higher and nearly an order of magnitude speedup as compared with the original algorithm using force constants for water and formaldehyde.     

基态SiCO体系的分析势能函数

在从头计算的基础上,对基态SiCO体系的全势能表面用多体项展式方法进行优化,确定了分析势能函数.该势能函数准确再现了基态SiCO(X3Σ-)和SiOC( X3Σ-)的线性结构和能量,正确反映了SiCO(X3Σ-)和SiOC(X3Σ- )异构体的离解通道.     

Potential energy surfaces of ozone in the ground state

Equilibrium parameters of ozone, such as equilibrium geometry structure parameters, force constants and dissociation energy are presented by CBS-Q {\it ab initio} calculations. The calculated equilibrium geometry structure parameters and energy are in agreement with the corresponding experimental values. The potential energy function of ozone with a C离解能;空气;能量表面;地面ozone, potential energy surface, barrier, dissociation energyProject supported by the National Natural Science Foundation of China (Grant Nos~10376021 and 10676025), and the Scientific Research Fund of Sichuan Provincial Education Department, China (Grant No~2006A131).2006-10-08Equilibrium parameters of ozone, such as equilibrium geometry structure parameters, force constants and dissociation energy are presented by CBS-Q ab initio calculations. The calculated equilibrium geometry structure parameters and energy are in agreement with the corresponding experimental values. The potential energy function of ozone with a C2v symmetry in the ground state is described by the simplified Sorbie-Murrell many-body expansion potential function according to the ozone molecule symmetry. The contour of bond stretching vibration potential of an O3 in the ground state, with a bond angle （θ） fixed, and the contour of O3 potential for O rotating around O1-O （R1）, with O1-O bond length taken as the one at equilibrium, are plotted. Moreover, the potentials are analysed.     

N2HF体系的结构与势能函数

用QCISD/6-311++G方法对N2HF体系进行优化得到其基态的平衡几何结构,属于C∞v构型,(1∑)态.计算表明N2HF分子是一特殊的van der Waals分子.应用多体项展式方法,导出了N2HF分子的解析势能函数,该函数正确的复现了N2HF体系的平衡结构及能量变化.势能面的静态特征表明:N2+HF→N2-HF反应是一个有阈能的反应,即是需活化能的反应,反应过程需克服144.21 kJ/mol的势垒.然后,就N2HF→N2+HF反应机理进行了讨论.     

Ag2La分子的结构与势能函数

采用密度泛函理论DFT中的UB3LYP方法,对Ag2La分子的结构进行优化,得到Ag2La分子基态结构为具有C2v对称性的弯曲结构,电子态为2A1,结合能为3.48eV。采用最小二乘法拟合出Ag2和AgLa分子的Murrell-Sorbie势能函数,在此基础上推导出光谱数据和力常数;通过多体展示理论导出基态Ag2La分子的势能函数,其等值势能图准确再现了Ag2La分子的结构特征及其势阱深度与位置。     

Ag2La分子的结构与势能函数

采用密度泛函理论DFT中的UB3LYP方法,对Ag2La分子的结构进行优化,得到Ag2La分子基态结构为具有C2v对称性的弯曲结构,电子态为2A1,结合能为3.48eV。采用最小二乘法拟合出Ag2和AgLa分子的Murrell-Sorbie势能函数,在此基础上推导出光谱数据和力常数;通过多体展示理论导出基态Ag2La分子的势能函数,其等值势能图准确再现了Ag2La分子的结构特征及其势阱深度与位置。     

Pu2+2 分子离子的结构与势能函数

使用密度泛函B3LYP方法对Pu2+2分子离子进行了理论研究,结果表明,Pu2+2分子离子是亚稳定结构,基态电子状态为 13Σg,势能函数可以用Z-W函数来表征,并首次计算获得基态分子离子的力常数和光谱数据.     

Collective octupole vibration and proton single-particle levels in zirconium nuclei

Self-energy correction to the shell model single-particle motion, arising from the excitation of octupole vibration in the intermediate state, accounts quite well for the energy shifts of the 2p _1/2 and 1g _9/2 proton orbits in zirconium nuclei.     

A refined potential energy function for the electronic ground state of H2Se

The potential energy surface for the electronic ground state of the hydrogen selenide molecule has been determined previously by Jensen and Kozin [J. Mol. Spectrosc. 160 (1993) 39] in a fitting to experimental data by means of the MORBID computer program. We report here a further refinement of this surface, also made with the MORBID program. With the refined potential surface, we can make predictions of rotation-vibration transition wavenumbers for H₂Se, D₂Se, and HDSe, and with these predictions we can assign weak spectra of these molecules. We assign here two very weak bands of HD⁸⁰Se, ν₁+ν₂+ν₃ and 2ν₁+ν₃. The refinement of the potential energy surface was made possible because (1) the number of vibrational states characterized experimentally for various isotopomers of H₂Se has approximately doubled since 1993, and (2) we now have access to larger computers with which we can fit energy spacings of states with J?8, whereas Jensen and Kozin could only use J?5. In the present work, we fitted rotation-vibration energy spacings associated with 24 vibrational states of H₂⁸⁰Se with v₁?6, v₂?3, and v₃?2; 11 vibrational states of D₂⁸⁰Se with v₁?2, v₂?3, and v₃?2, and 17 vibrational states of HD⁸⁰Se with v₁?3, v₂?3, and v₃?3. The input data set comprised 3611 energy spacings. In the fitting, we could usefully vary 29 potential energy parameters. The standard deviation of the fitting was 0.12 cm⁻¹ and the root-mean-square deviation for 49 vibrational term values was 0.59 cm⁻¹.     

Linewidths of ammonia in collisions with He: Calculations from an ab initio potential

We present semiclassical calculations based on the Robert-Bonamy formalism of collisional broadening coefficients of ammonia by collision with He at room temperature. Calculations have been performed with the accurate ab initio potential of Hodges and Wheatley. The calculated line widths are compared to the available experimental data and a satisfactory agreement is found, although the model contains no adjustable parameters. However the calculations also exaggerate the K dependence of the broadenings, especially for lines with K = J − 1 or K = J.     

人为扰动的模型势函数及其动力学特征

目前,结合高精度从头算方法和全维量子动力学计算,对四原子气相反应,理论计算可以获得与实验结果完全一致的结果。一般情况下,一个精确的量子动力学模拟需要一个精确的势能面,但是在实际的计算当中,势能面的拟合误差是不可避免的。在本文中,我们考察了在模型势能面外加各种扰动时的动力学反应行为,在2维的势能面上进行了量子动力学计算。反应速率常数对近反应能垒区域或最小能量反应路径上的干预是较为敏感的,但是在势能面上的其它地方加入的外加干扰对反应速率影响不大。本文给出一个比较重要的和比较简单的结论,在量子动力学模拟中,在精确的势能面上增加相关的扰动,会帮助我们更深入地理解给定类型的反应,对于一个特定体系,其精确势能面上可以作为一个模型体系研究。