The orbital minimization method for electronic structure calculations with finite-range atomic basis sets

The implementation of the orbital minimization method (OMM) for solving the self-consistent Kohn–Sham (KS) problem for electronic structure calculations in a basis of non-orthogonal numerical atomic orbitals of finite-range is reported. We explore the possibilities for using the OMM as an exact cubic-scaling solver for the KS problem, and compare its performance with that of explicit diagonalization in realistic systems. We analyze the efficiency of the method depending on the choice of line search algorithm and on two free parameters, the scale of the kinetic energy preconditioning and the eigenspectrum shift. The results of several timing tests are then discussed, showing that the OMM can achieve a noticeable speedup with respect to diagonalization even for minimal basis sets for which the number of occupied eigenstates represents a significant fraction of the total basis size (>15%). We investigate the hard and soft parallel scaling of the method on multiple cores, finding a performance equal to or better than diagonalization depending on the details of the OMM implementation. Finally, we discuss the possibility of making use of the natural sparsity of the operator matrices for this type of basis, leading to a method that scales linearly with basis size.     

Efficient treatment of collisions in simulation codes for heavy-ion reactions

This paper presents a technique for the modelling of collisions in simulation codes for the approximation of the relativistic Boltzmann-Uehling-Uhlenbeck equation. This equation is used to describe nuclear matter, in particular particle interactions during heavy-ion collisions. The technique presented is particularly designed to treat collisions efficiently on modern supercomputers.     

PHASE-OTI: A pre-equilibrium model code for nuclear reactions calculations

The present work focuses on a pre-equilibrium nuclear reaction code (based on the one, two and infinity hypothesis of pre-equilibrium nuclear reactions). In the PHASE-OTI code, pre-equilibrium decays are assumed to be single nucleon emissions, and the statistical probabilities come from the independence of nuclei decay. The code has proved to be a good tool to provide predictions of energy-differential cross sections. The probability of emission was calculated statistically using bases of hybrid model and exciton model. However, more precise depletion factors were used in the calculations. The present calculations were restricted to nucleon-nucleon interactions and one nucleon emission.

Program summary

Program title: PHASE-OTICatalogue identifier: AEDN_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEDN_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 5858No. of bytes in distributed program, including test data, etc.: 149 405Distribution format: tar.gzProgramming language: Fortran 77Computer: Pentium 4 and Centrino DuoOperating system: MS WindowsRAM: 128 MBClassification: 17.12Nature of problem: Calculation of the differential cross section for nucleon induced nuclear reaction in the framework of pre-equilibrium emission model.Solution method: Single neutron emission was treated by assuming occurrence of the reaction in successive steps. Each step is called phase because of the phase transition nature of the theory. The probability of emission was calculated statistically using bases of hybrid model [1] and exciton model [2]. However, more precise depletion factor was used in the calculations. Exciton configuration used in the code is that described in earlier work [3].Restrictions: The program is restricted to single nucleon emission and nucleon-nucleon interactions.Running time: 5-30 minutesReferences:

[1]

M. Blann, Phys. Rev. Lett. 27 (1971) 337.

[2]

E. Gadioli, E.G. Erba, J.J. Hogan, Phys. Rev. C 16 (1977) 1404-1424.

[3]

E.K. Elmaghraby, Phys. Rev. C 78 (2008) 014601.

     

Comparison of heavy-ion induced SEU for D- and TMR-flip-flop designs in 65-nm bulk CMOS technology

Heavy ion experiments were performed on D flip-flop （DFF） and TMR flip-flop （TMRFF） fabricated in a 65-nm bulk CMOS process. The experiment results show that TMRFF has about 92% decrease in SEU cross- section compared to the standard DFF design in static test mode. In dynamic test mode, TMRFF shows much stronger frequency dependency than the DFF design, which reduces its advantage over DFF at higher operation frequency. At 160 MHz, the TMRFF is only 3.2~ harder than the standard DFF. Such small improvement in the SEU performance of the TMR design may warrant reconsideration for its use in hardening design.     

Exact and heuristic algorithms for balancing transfer lines when a set of available spindle heads is given

A balancing problem for paced tandem transfer lines with several spindle heads at each station is considered. A spindle head executes a block of operations. The set of all available spindle heads as well as the operations executed by each spindle head, the spindle head times and costs are known. There are operations with several spindle head candidates. The problem at the line design stage consists in the choice of spindle heads from the given set and their assignment to workstations. The goal is to minimize the line cost while satisfying the precedence, inclusion and exclusion constraints. An exact algorithm based on a mixed integer programming approach is developed. Two types of new heuristic algorithms are also suggested. One of them step‐by‐step assigns randomly spindle heads to a current workstation. The second uses depth‐first search techniques. Experimental results are reported.     

Exact and numerical solutions for unsteady heat and mass transfer problem of Jeffrey fluid with MHD and Newtonian heating effects

The combined heat and mass transfer of unsteady magnetohydrodynamic free convection flow of Jeffrey fluid past an oscillating vertical plate generated by thermal radiation and Newtonian heating is investigated. The incompressible fluid is electrically conducting in the presence of a uniform magnetic field which acts in a direction perpendicular to the flow. Mathematical formulation of the problem is modeled in terms of partial differential equations with some physical conditions. Some suitable non-dimensional variables are introduced to transform the system of equations. The dimensionless governing equations are solved analytically for exact solutions using the Laplace transform technique. Numerical solutions of velocity are obtained via finite difference scheme. Graphical results for velocity, temperature and concentration fields for various pertinent parameters such as material parameter of Jeffrey fluid \(\lambda_{1}\), dimensionless parameter of Jeffrey fluid \(\lambda\), Newtonian heating parameter \(\xi\), phase angle \(\omega t\), Grashof number \(Gr\), modified Grashof number \(Gm\), Hartmann number or magnetic parameter \(Ha\), Prandtl number \(Pr\), radiation parameter \(Rd\), Schimdt number \(Sc\) and dimensionless time \(t\) are displayed and discussed in detail. This study showed that the magnetic field resists the fluid flow due to the Lorentz force, whereas the thermal radiation and Newtonian heating parameters lead to the enhancement of velocity and temperature fields. Present results are also compared with the existing published work, and an excellent agreement is found.