Effect of 0h11/2 Level on Shell Model Calculations of ^105Sb and ^107Sb

The full and reduced shell model calculations have been carried out for the light odd-even ^105Sb and ^107Sb isotopes. The model space has been chosen as 1d5/2, 0g7/2, 1d3/2, 2s1/2, and 0h11/2 for the full calculations and excluded 0h11/2 for the reduced calculations. The reduced shell model calculations of ^105Sb and ^107Sb isotopes are presented for the first time. We obtain the energy spectra for the ^105Sb and ^107Sb isotopes in the full and reduced model space by using CD-Bonn two-body effective nucleon-nucleon interaction. The resulting energy spectra are compared to the experimental results to understand the effect of the 0h11/2 level on the shell model calculations. We draw conclusions about the right model space in the shell model calculations for the isotopes around the N =Z= 50 region of the periodic table.     

Two-δ- Function Generalized Plasma Pole Model for First Principle Calculations of Quasiparticle Energies in Many-Electron Systems

To evaluate the dynamical effects of the screened interaction in the calculations of quasiparticle energies in many-electron systems a two-δ-function generalized plasma pole model (GPP) is introduced to simulate the dynamical dielectric function. The usual single δ-function GPP model has the drawback of over simplifications and for the crystals without.the center of symmetry is inappropriate to describe the finite frequency behavior for dielectric function matrices. The discrete frequency summation method requires too much computation to achieve converged results since ab initio calculations of dielectric function matrices are to be carried out for many different frequencies. The two-δ GPP model is an op timization of the two approaches. We analyze the two-δ GPP model and propose a method to determine from the first principle calculations the amplitudes and effective frequencies of these δ functions. Analytical solutions are found for the second order equations for the parameter matrices entering the model. This enables realistic applications of the method to the first principle quasiparticle calculations and makes the calculations truly adjustable parameter free.     

Near-threshold boson pair production in the model of smeared-mass unstable particles

Near-threshold production of boson pairs is considered within the framework of the model of unstable particles with smeared mass. We describe the principal aspects of the model and consider the strategy of calculations including the radiative corrections. The results of calculations are in good agreement with LEP II data and Monte-Carlo simulations. Suggested approach significantly simplifies calculations with respect to the standard perturbative one.     

Shell model approach to collectivity in pseudo spin-orbit coupling

A technique is described for shell model calculations in the newly suggested k-i representation of single particle states. The technique allows microscopic calculations for the structure of medium and heavy nuclei in spaces which are truncated in an analogy with the assumptions of the interacting boson model (IBM). The present technique incorporates all the power and generality of standard shell model calculations and provides a unified approach to even-even, even-odd and odd-odd nuclei.     

A simple shell model calculation of differential ionic relaxations at the (100) surfaces of NaCl structure alkali halides

The rumpling of anions and cations in the (100) surface layer of various rockSalt-structure alkali halides has been calculated using a simple extension of an original model due to Verwey. It is shown that reasonable agreement with the results of more sophisticated calculations can be obtained when the interionic potentials used in the calculations are derived from shell model calculations based on the elastic properties of the various materials. The idea of a “Surface ionic polarisability” is proposed, and the results of its use in rumpling calculations compared with those obtained using conventional “bulk” polarisabilities.     

Misalignment of oriented nuclei in ferromagnets

Two atomic model calculations are carried out in order to understand misalignment of nuclei in ferromagnets suggested by various authors. It is concluded that an unlikely large exchange interaction is needed in these model calculations to explain a substantial misalignment.     

A general pseudopotential model for molecules with many valence electrons

Criteria are discussed for the practical application of ‘valence-electron only’ calculations aimed at simulating ab initio all-electron calculations on molecules containing heavy atoms with many core electrons. A theoretical model is outlined based on the use of pseudopotentials derived from atomic SCF calculations. The model has been used in calculations for NaH, Na₂, H₂S, S₂, H₂S₂, HCl, Cl₂ and NaCl, and has been tested by comparison with reference all-electron calculations. Most of these tests employ double-zeta basis sets and SCF wavefunctions, although polarization functions and complete valence-electron CI wavefunctions have been used in some cases. The model is generally successful for ground-state equilibrium structures, charge distributions and orbital energies.     

Simulation of Spin-3/2 Blume-Capel Model on a Cellular Automaton with Heating and Cooling Algorithm

The spin-3/2 Blume-Capel model is studied using the heating and cooling algorithms improved from the Creutz cellular automaton (CCA). The calculations are done on various sizes of the simple cubic lattice in the 0≦D/J≦5 parameter region. The phase diagram of the model and temperature variation of the thermodynamic quantities are obtained. We confirm the existence of a critical end point within the heating calculations. However, in contrast to the heating
calculations, we do not obtain the first-order line at low temperature with cooling algorithm calculations. The results are compared with those of other theories.     

“Exact” shell model calculations and linked nuclear effective interactions

It is shown that so-called “exact” shell model calculations of spectra (diagonalizations) contain important unlinked terms which are due to space truncation. These terms render less interesting a comparison between the “exact” calculation of spectra and model space calculations with effective interactions containing linked terms only. The spectral calculations were performed in mass 6. The lowest order unlinked terms which arise in the “exact” calculation were calculated in mass 6 and mass 18.     

An efficient numerical method for time-dependent NLTE radiation transfer

We present a numerical method for performing coupled time-dependent radiation transfer and atomic rate equation calculations. The method incorporates the desirable features of time-dependent, non-local thermodynamic equilibrium (NLTE) radiation transfer calculations. It has the advantage that it allows existing time-dependent calculations to be adapted to model time dependent effects. The approximations which are used are discussed.Calculations have been performed for a highly ionised silicon plasma with a single optically thick line. The line is taken to have a top-hat profile which is independent of position. Although the model is simple, it serves to illustrate some important features of time-dependent calculations.     

Persistent currents in mesoscopic rings

The discrepancy between measured values of the persistent current in mesoscopic rings and theoretical calculations based upon the model of independent electrons moving in a random potential is discussed. Some attempts at including the Coulomb interaction between electrons are reviewed, and results of model calculations are presented.     

Aluminum Hugoniot from model calculations including semicore electrons based on density functional theory

We present a method to obtain Hugoniot from model calculations based on density functional theory, and apply the method to aluminum Hugoniot. Technological advances have extended the experimental research of high energy density physics, and call for quantitative theoretical analysis. However, direct computation of Hugoniot from density functional theory is very difficult. We propose two step calculations of Hugoniot from density functional theory. The first step is molecular dynamics simulations with an ambient temperature for electrons. The second step is total energy calculations of a crystal with desired high temperatures for electrons and with the ambient temperature for electrons. We treated the semicore 2s and 2p electrons of aluminum as valence electrons only for the total energy calculations of the aluminum crystal. The aluminum Hugoniot from our model calculations is in excellent agreement with available experimental data and the previous density functional theory calculations in the literature.     

基于关联基的壳模型截断计算

提出了一种新的用于壳模型截断计算的基矢空间的构建方法,即关联基的方法。关联基是利用壳模型中每个粒子数分布下哈密顿量的本征态作为基矢。在此基矢之上,可以很自然地通过考虑能量相对较低的关联基矢进行相应的截断计算。当所有的关联基矢都被考虑时,计算结果回到一般jj耦合给出的结果。最后,对关联基下壳模型的计算与标准的壳模型计算进行了比较,计算结果表明,关联基下壳模型能量和波函数有着良好的收敛性,同时表明关联基计算的有效性。     

Band crossing and surface states in solids

A symmetry criterion for the existence of surface states in model calculations in solids is derived. The criterion applies to surfaces that coincide with symmetry planes of the ideal crystal. A detailed analysis is carried out for one-dimensional model calculations and it is shown how band crossing can be interpreted in the framework of the crystal symmetry.     

Treatment of continua in the shell-model theory of nuclear reactions

It is shown that by a suitable choice of the bound- and continuum-state functions used to perform shell-model calculations, the continuum-continuum interaction may be minimized. Approximate expressions for the scattering matrix elements are derived that are easily evaluated by simple extensions of the conventional shell-model calculations for bound states. Numerical calculations are performed for neutron scattering from ¹²C within the framework of the deformed rotor model and compared with exact coupled-channel calculations.     

Ab initio study of 40Ca with an importance-truncated no-core shell model

We propose an importance truncation scheme for no-core shell model or configuration interaction approaches, which enables converged calculations for nuclei well beyond the p shell. It is based on an a priori measure for the importance of individual basis states constructed by means of many-body perturbation theory. Only the physically relevant states of the no-core model space are considered, which leads to a dramatic reduction of the basis dimension. We analyze the validity and efficiency of this truncation scheme using different realistic nucleon-nucleon interactions and compare to conventional no-core shell model calculations for 4He and 16O. Then, we present first converged calculations for the ground state of 40Ca within no-core model spaces including up to 16 PlanckOmega excitations using realistic low-momentum interactions. The scheme is universal and can be easily applied to other quantum many-body problems.     

Estimation of particle size distributions obtained by gas phase processes

Nanoparticles intended for high value added applications often require special size distributions. Based on model calculations, this article compares the particle size distributions obtained with conventional and plasma processes. The model is based on an estimation of the probability for collisions; either for neutral or equally charged particles, whereas the growth of the particles is calculated using a model derived from Markov chains. The results of these calculations confirm the empirical knowledge that, under the special conditions of particles carrying electric charges of equal sign, plasma processes deliver products with the narrowest particle size distribution. Synthesis of extremely small particles with conventional processes leads to a significant residue of unreacted precursor. This finding is important in cases of expensive educts. The results of these model calculations are in perfect agreement with experimental findings.     

Monte Carlo and cell model calculations for the solid—fluid phase behaviour of the triangle-well model

Monte Carlo simulations and cell model calculations are reported for the vapour-liquid and solid-liquid phase behaviour of the triangle-well model system. The behaviour is examined as a function of the range of the triangle-well attraction, from 1.05 to 2.5 times the diameter of the hard core of the potential. Cell model calculations indicate that the stable solid is almost always face-centred cubic (fcc), except for a small set of conditions where hexagonal close-packed (hcp) is favoured. This outcome differs markedly from a much earlier study performed for the square-well model potential, where a much richer phase diagram was observed, with significant regions of stability for hep and body-centred cubic (bcc) phases. Monte Carlo simulations indicate that the cell model calculations represent well the true phase behaviour for this model system. The differing behaviour between the triangle-well and square-well models indicates an important role for the flatness of the potential well in governing the stability of hcp and bcc phases relative to the fcc phase.     

Reactions leading to the 7Li and 8Li systems: Shell model and R-matrix calculations

Level energies and reduced width amplitudes obtained from shell model calculations for ⁷Li and ⁸Li are incorporated into multilevel, multichannel R-matrix calculations of cross sections for reactions leading to these compound systems. With changes to a very few of the large number of parameters obtained from the model calculations, cross sections for eight reactions leading to the ⁷Li system and for five reactions leading to the ⁸Li system are calculated. For reactions where data are available, the calculated cross sections are in good agreement with experimental measurements. Comparisons of the present work to other structure studies are made and suggestions as to possible improvements in the model calculations are given. The applicability of the technique used here to other nuclear structure studies is discussed.