He-CO相互作用势及散射截面的理论研究

利用改进的MS势模型拟合出了He-CO体系一种形式简单的各向异性相互作用势,应用拟合的势能,采用全量子力学的密耦方法计算了基态氦原子和CO分子碰撞的散射截面,分析并总结了散射截面的变化规律。计算结果表明拟合势能不但表达形式简洁,而且较好的描述了He-CO系统相互作用的特征。为进一步研究He与CO微观碰撞机理有一定的参考价值。     

He-CO相互作用势及散射截面的理论研究

利用改进的MS势模型拟合出了He-CO体系一种形式简单的各向异性相互作用势,应用拟合的势能,采用全量子力学的密耦方法计算了基态氦原子和CO分子碰撞的散射截面,分析并总结了散射截面的变化规律。计算结果表明拟合势能不但表达形式简洁,而且较好的描述了He-CO系统相互作用的特征。为进一步研究He与CO微观碰撞机理有一定的参考价值。     

A relativistic coupled-cluster interaction potential and rovibrational constants for the xenon dimer

An accurate potential energy curve has been derived for the xenon dimer using state-of-the-art relativistic coupled-cluster theory up to quadruple excitations accounting for both basis set superposition and incompleteness errors. The data obtained is fitted to a computationally efficient extended Lennard-Jones potential form and to a modified Tang–Toennies potential function treating the short- and long-range part separately. The vibrational spectrum of Xe₂ obtained from a numerical solution of the rovibrational Schrödinger equation and subsequently derived spectroscopic constants are in excellent agreement with experimental values. We further present solid-state calculations for xenon using a static many-body expansion up to fourth-order in the xenon interaction potential including dynamic effects within the Einstein approximation. Again we find very good agreement with the experimental (face-centred cubic) lattice constant and cohesive energy.     

The volume contribution of the ion-ion optical potential from realistic complex nucleon-nucleon interaction

The real and imaginary parts of the optical model potential for several pairs of magic nuclei have been calculated by a double folding procedure. The complex effective interaction is calculated from the Reid soft core potential by solving the Bethe-Goldstone equation in two colliding nuclear matters. The calculated potentials were approximated with a Woods-Saxon shape. We studied the dependence of the parameters of these Woods-Saxon forms on the masses of the interacting nuclei.     

氦原子与一氧化碳分子各向异性势的计算研究

本文用高精度的量子力学ab initio方法计算了氦原子与一氧化碳分子相互作用各向异性势能面,通过三重激发校正耦合簇、二次组态相互作用等方法和不同基组的计算结果比较,并采用BSSE方法消除了基组重叠误差,得到了氦原子与一氧化碳分子体系相互作用各向异性势,然后采用精确度较高的密耦（Close-Coupling）近似方法,研究了氦原子与一氧化碳分子碰撞的散射截面,通过计算得出了该体系碰撞激发微分截面和分波截面,计算得到的微分截面数据与实验值符合较好,说明本文得到的势能面是准确的.     

Self-assembly of monatomic complex crystals and quasicrystals with a double-well interaction potential

For the study of crystal formation and dynamics, we introduce a simple two-dimensional monatomic model system with a parametrized interaction potential. We find in molecular dynamics simulations that a surprising variety of crystals, a decagonal, and a dodecagonal quasicrystal are self-assembled. In the case of the quasicrystals, the particles reorder by phason flips at elevated temperatures. During annealing, the entropically stabilized decagonal quasicrystal undergoes a reversible phase transition at 65% of the melting temperature into an approximant, which is monitored by the rotation of the de Bruijn surface in hyperspace.     

The determination of the model interaction potential parameters from a comparison of experimental and calculated ion ranges in an amorphous substance

Parameters of the model atomic interaction potential are suggested to be determined by comparing the experimental and analytical values of projective ion ranges. The parameters were found for the interaction of Bi, Pb, Au, Yb, Er, Eu, Cs, Xe, Sn, Rb, Kr, Ga, and Cu ions with carbon and boron atoms.     

The Skyrmion Skyrmion interaction and the meson exchange model for the NN potential

The properties of nucleon-nucleon (NN) potentials derived from the Skyrme model are investigated compared to those of typical One-Boson-Exchange (OBE) models, For that purpose the NN as well as the nucleon-antinucleon (N¯N) potentials are evaluated for the isoscalar central channel, the isovector spin channel, and the isovector tensor channel. A comparison of NN and N¯N interactions allows a separation into terms with positive and negativeG-parity and therefore a detailed comparison with the properties of the OBE model. This analysis is performed using the classical Lagrangian of the Skyrme model and considering an extension of this Lagrangian by a term of sixth order, which has recently been proposed. The results indicate that the extended Lagrangian yields an interaction which is quite consistent with the OBE picture. The extended model, however, is much more sensitive to the values of the parameters and the approximations being used for the evaluation of the field for two baryons.     

The rovibrational levels of ammonia

In this paper we report variational rovibrational studies on ammonia and its isotopomers. We use six internal coordinates (one of which describes the umbrella motion). The expansion functions are products of one-dimensional functions of these internal coordinates, multiplied by appropriate functions of the Euler angles to describe the rotational motion. We use a previously published high accuracy six-dimensional potential energy surface [LEONARD, C., HANDY, N. C., CARTER, S., and BOWMAN, J. M., 2002, Spectrachim. Acta, 58, 825]. We derive the full kinetic energy operator for the rovibrational motion in these coordinates. This operator has been completely checked to give a hermitian secular matrix. All matrix elements are evaluated numerically by quadrature. The symmetry of the expansion functions is fully described in D_3h, C_2v and C_s. It is not possible to perform the calculations in D_3h, but complete degeneracy in the appropriate levels is obtained with the C_2v program. The algebraic complexity of this program has been far greater than for any other variational study we have undertaken for a tetra-atomic molecule.

We present J = 0, 1, 2 energy levels for the experimentally observed band origins of NH₃, and J = 0, 1 energy levels for the ground state and fundamentals of NH₂D, ND₂H and ND₃. For the asymmetric isotopomers, identical results are obtained for both C_2v and C_s, thus confirming the validity of the method. The levels we obtain are completely converged. Agreement with observation is of the order of 0.5% (of course being dependent upon the accuracy of the potential energy surface); therefore the ordering of the rotational levels and their splitting is completely predicted and understood.     

Two-channel separable potential model for the low-energy hyperon-nucleon interaction

A two-channel separable potential model is given such that the T-matrix is given in the form of a N/D matrix. This model is used to examine the relationships between the three different definitions for a resonance in the two-channel problem, particularly for a ³S₁ Λp resonance. In order to obtain a phenomenological hyperon-nucleon (YN) scattering T-matrix in the present model, a least-squares fit is performed to the existing available data for the $\text{I =}\text{1}\text{2}\text{YN}$ scattering cross sections and angular distributions at low energies using the s- and p-wave N/D solutions which carry sixteen independent parameters. Several solution sets of potential parameters are found, for which we can obtain good fits to the Λp → Λp, Σ^?p → Λn and ΣN → ΣN data, particularly to the cross-section data for these processes. The p-wave contributions are estimated, and particularly the possibility of p-wave YN resonances is pointed out for the solutions for which we do not assume a ³₁ Λp resonance.     

On the effective medium model for particles with a complex structure

We consider a generalization of the effective medium approximation to the case of matrices containing macroscopically inhomogeneous particles with an arbitrary structure (cermet topology). The form of the result is determined to a considerable extent by the heuristic choice of effective cells used to estimate the field and induction values averaged over the volume. The simplest choice of a particle in an unperturbed field as a cell leads to the Maxwell–Garnett approximation, while the self-consistent effective medium approximation corresponds to the replacement of the unperturbed field by the mean field. As an example, we describe particles with a shell, as well as statistically anisotropic media with a single preferred direction.     

Ne-BeH体系的相互作用势和能级结构的理论研究

本文对Ne-BeH体系采用单双迭代(包括非迭代三重激发)耦合簇理论CCSD(T)方法,对Be , H 和 Ne原子采用aug-cc-pVQZ基组和3s3p2d1f1g中心键函数.利用非线性最小二乘法拟合该理论水平下的相互作用能,得到了Ne-BeH弱相互作用体系在冻结BeH键长情况下的二维的全程势能面,在 和 处存在一全局最小值-34.43607 .利用该势能面,计算了Ne-BeH体系的J=0-9的能级结构.以期对Ne-BeH的相关的实验和理论研究提供必要的参考和借鉴.     

The potential of quark-antiquark interaction

A phenomenological potential of quark-antiquark interaction (1) is considered within the quasiclassical framework. It is shown that the Van Royen-Weisskopf relation has a different origin for pseudoscalar and vector mesons. For pseudoscalar mesons, it follows from the SU(4) symmetry of strong interactions, while for vector mesons, the Van Royen-Weisskopf relation is a consequence of a certain dynamical mechanism of quark-antiquark interaction. On the basis of a nonrelativistic quark model it is shown that the parameter takes the same value =0.21 (GeV)² for different quark-antiquark systems. Taking this value of , the energy spectra of quark-antiquark (c¯c)-, (b¯b)-, and (t¯t)-systems are constructed, and the partial widths of the decays V⁰e⁺e^– of these levels, are determined. A condition for the occurrence of the first negative-energy level of a quark-antiquark (q₁¯q₂)-system is found. A comparison with the experiment is made.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 104–108, April, 1984.In conclusion, I want to thank Yu. P. Nikitin and I. L. Rozental' for useful discussions and critical comments.     

Ne-BeH体系的相互作用势和能级结构的理论研究

本文对Ne-BeH体系采用单双迭代(包括非迭代三重激发)耦合簇理论CCSD(T)方法,对Be , H 和 Ne原子采用aug-cc-pVQZ基组和3s3p2d1f1g中心键函数.利用非线性最小二乘法拟合该理论水平下的相互作用能,得到了Ne-BeH弱相互作用体系在冻结BeH键长情况下的二维的全程势能面,在 和 处存在一全局最小值-34.43607 .利用该势能面,计算了Ne-BeH体系的J=0-9的能级结构.以期对Ne-BeH的相关的实验和理论研究提供必要的参考和借鉴.     

Ab initio study for the intermolecular interaction potential surface of Ar-N2 complex

The intermolecular interaction potentials of van der Waals Ar-N2 complex have been studied by ab initio calculations using the single and double excitation coupled cluster [CCSD(T)] theory with perturbative triples correction. The full counterpoise method is applied to correct the basis set superposition error (BSSE). It is found that the T-shaped structure is the most stable conformation with the well depth De of 12.40 meV at the minimum distance Rm of 3.70 Å. The calculated anisotropic values for Rm, R0 and De are 0.56 Å, 0.54 Å and 2.68 meV, respectively. Compared with those obtained by others, our calculated PES seems to be in better agreement with experiments.     

The effective interaction in a nuclear model

The effective interactionU belonging to a given subspace ofn unperturbed model functions can be related to the free nucleon-nucleon interaction by means of an exact integral equation. The conditions for a Born-v. Neumann expansion ofU and for an approximation by a slowly energy dependent interaction with adjustable parameters are investigated. It appears that effective interactions which have been used successfully in shell model calculations of bound state properties do not necessarily describe the actual dynamics of a nucleus.     

Triton with N---N potential from a quark model

The properties of the three-nucleon bound state are studied employing a nucleon-nucleon potential deduced from the quark cluster model in a five-channel Faddeev calculation. The triton is bound about 0.2–0.3 MeV more than would be expected from conventional meson-exchange models.