| 1. |
- Brickner, R.G, et al.
(författare)
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QCD on the Connection Machine: Beyond-Lisp
- 1991
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Ingår i: Computer Physics Communications. - 0010-4655 .- 1879-2944. ; 65, s. 39-51
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Tidskriftsartikel (refereegranskat)abstract
- We report on the status of code development for a simulation of quantum chromodynamics (QCD) with dynamical Wilson fermions on the Connection Machine model CM-2. Our original code, written in * Lisp, gave performance in the near-GFLOPS range. We have rewritten the most time-consuming parts of the code in the low-level programming system CMIS, including the matrix multiply and the communication. Current versions of the code run at approximately 3.6 GFLOPS for the fermion matrix inversion, and we expect the next version to reach or exceed 5 GFLOPS.
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| 2. |
- Edvardsson, Sverker, et al.
(författare)
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An atomic program for energy levels of equivalent electrons: lanthanides and actinides
- 2001
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Ingår i: Computer Physics Communications. - 0010-4655 .- 1879-2944. ; 133:2/3, s. 396-406
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Tidskriftsartikel (refereegranskat)abstract
- A program written in C is presented to carry out brute force calculations in order to derive energy levels for an equivalent electronic configuration. Relativistic effects are partly neglected except for the spin-orbit interaction. Since the main relativistic effects are indirect, i.e. causing a contraction of the core which in turn causes the outer shells to expand, they are included to a high degree through the use of appropriate Slater integrals. The program is especially useful for primarily unfilled f-shells of the rare-earth or actinide ions. Modifications of the program to include spin−spin, spin−other orbit, Breit interaction etc. is straight forward. The program is also general in the sense that there is no need to find out or generate any Racah coefficients of fractional parentage. The complete energy matrix is diagonalized with all operators interacting simultaneously thus allowing mixing of all quantum numbers. This result in all energy eigenvalues and eigenvectors that in turn for example are partly responsible for the polarized dipole, quadrupole, … transitions within the unfilled shell. Free ion configuration interaction is accounted for through the use of standard CI operators. The Stark splitting can be studied via the standard crystal field Hamiltonian. Magnetic field influence on the energy levels may also be studied.
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| 3. |
- Ishio, H., et al.
(författare)
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Wave function statistics for mesoscopic transport through chaotic open billiards : Time reversibility, space reciprocity breaking and statistical crossover
- 2001
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Ingår i: Computer Physics Communications. - 0010-4655 .- 1879-2944. ; 142:1-3, s. 64-70
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We investigate the probability distributions and spatial correlations of the local densities of electron wave functions for ballistic transport through mesoscopic chaotic open billiards. By quantitative comparison between our accurate fully-quantal calculations with theoretical expressions, we find wave-statistical behaviors intrinsically different from those in closed systems. It is shown that chaotic-scattering wave functions in open systems can be universally interpreted in terms of statistically independent real and imaginary random fields together with breaking of the endowed space reciprocity, resulting in the same wave function statistics as in the time-reversal symmetry-breaking crossover regime in closed systems. © 2001 Elsevier Science B.V. All rights reserved.
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| 4. |
- Jaun, André, et al.
(författare)
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Iterative solution of global electromagnetic wavefields with finite elements
- 2001
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Ingår i: Computer Physics Communications. - 0010-4655 .- 1879-2944. ; 135:1, s. 74-81
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Tidskriftsartikel (refereegranskat)abstract
- The time-independent Maxwell equations are solved iteratively in 2D geometry fur 3D global waves in plasma physics. Krylov space methods, such as the generalized- or the quasi-minimal residuals (GMRES or QMR), are applied together with an incomplete factorization (ILU) preconditioning to a formulation using nodal elements for the electromagnetic scalar and vector potentials. The plasma response is represented as a complex, frequency dependent, dielectric tensor operator and can be used for a variety of applications involving low frequency waves in a tokamak. The iterative approach does not only result in considerable memory savings, but it is also more efficient than a direct solution and paves the way for the parallelization of global wave and stability codes.
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| 5. |
- Johnsson, Lennart
(författare)
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Cyclic Reduction on a Binary Tree
- 1985
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Ingår i: Computer Physics Communications. - : Elsevier BV. - 0010-4655 .- 1879-2944. ; 37:1-3, s. 195-203
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Tidskriftsartikel (refereegranskat)abstract
- Ensembles of large numbers of processors tightly coupled into networks are of increasing interest. Binary tree interconnect has many favourable characteristics from a construction point of view, though the limited communication bandwidth between arbitrary processors poses a potential bottleneck. In this paper we present an algorithm for odd-even cyclic reduction on a binary tree for which the limited bandwidth does not increase the order of the computational complexity, compared to an ideal parallel machine. The complexity is 2 log2N with respect to arithmetic operations, and 3 log2N with respect to communication. The communication complexity compares favourably with the best previously published result, O(log22N). We also show that the benefits of truncated cyclic reduction are much greater for parallel reduction algorithms than for sequential algorithms. A reduction in the computational complexity proportional to the reduction in the number of reduction steps is possible.
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| 6. |
- Jönsson, Per, et al.
(författare)
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A program for computing weak and intermediate field Zemman splittings from MCHF wave functions
- 2002
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Ingår i: Computer Physics Communications. - : Elsevier. - 0010-4655 .- 1879-2944. ; 144:2, s. 188-199
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Tidskriftsartikel (refereegranskat)abstract
- Given electronic wave functions generated by the MCHF_CI program (LSJ format), this program calculates diagonal Landé g factors that determine separations of magnetic sublevels in weak external magnetic fields. In addition the program computes off-diagonal Landé g factors and constructs the total interaction matrix for an atom in a magnetic field. By diagonalizing the interaction matrix and plotting the eigenvalues as functions of the magnetic field, Zeeman structures beyond the weak field limit are obtained.
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| 7. |
- Levitina, Tatiana, et al.
(författare)
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On the Schrödinger equation in ellipsoidal coordinates
- 2000
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Ingår i: Computer Physics Communications. - : Elsevier. - 0010-4655 .- 1879-2944. ; 126:1-2, s. 107-113
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Tidskriftsartikel (refereegranskat)abstract
- Quantum scattering by a potential separable in ellipsoidal coordinates is investigated. If the potential vanishes at infinity fast enough, its scattering data – S-matrix, far field amplitude, and total cross-section – are expanded in perturbed Lamé wave functions.
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| 8. |
- Salek, Pawel
(författare)
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A wave-packet technique to simulate resonant X-ray scattering cross sections
- 2003
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Ingår i: Computer Physics Communications. - 0010-4655 .- 1879-2944. ; 150:2, s. 85-98
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Tidskriftsartikel (refereegranskat)abstract
- This article describes algorithms and a program implementation for wave packet calculations of resonant X-ray scattering cross sections of molecules with one active internal degree of freedom. The program uses a time-dependent formalism and a grid representation of the wave packets. The potentials of ground, core-excited and final states can be specified by analytical expressions or by discrete sets of energies on arbitrary grids allowing for interfacing with electronic structure packages. The theory on which the program is founded is briefly reviewed. The implemented numerical algorithm is described in detail together with usage instructions and a sample application.
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| 9. |
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| 10. |
- Thibert-Plante, Xavier, 1980-, et al.
(författare)
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A simple spectral algorithm for solving large-scale Poisson equation in 2D
- 2003
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Ingår i: Computer Physics Communications. - : Elsevier. - 0010-4655 .- 1879-2944. ; 154:2, s. 89-97
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Tidskriftsartikel (refereegranskat)abstract
- We show that it is possible with easy-to-program algorithms to reach spatial resolutions of the order of 108 grid points for computing the electric potential on 2D periodic lattices, such as the Si(111)7×7 surface. We have used a spectral Fourier technique and parallelized FFTs with OPEN_MP on SGI machines. This method can be easily extended to 3D.
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