Elsevier Science Home
Computer Physics Communications Program Library
Full text online from Science Direct
Programs in Physics & Physical Chemistry
CPC Home

[Licence| Download | New Version Template] aecc_v2_1.tar.gz(303 Kbytes)
Manuscript Title: A highly optimized code for calculating atomic data at neutron star magnetic field strengths using a doubly self-consistent Hartree-Fock-Roothaan method
Authors: C. Schimeczek, D. Engel, G. Wunner
Program title: HFFERII
Catalogue identifier: AECC_v2_1
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 185(2014)1498
Programming language: Fortran 95.
Computer: Cluster of 1-13 HP Compaq dc5750.
Operating system: Linux.
Has the code been vectorised or parallelized?: Yes, with MPI directives.
RAM: 1 GByte per node
Keywords: Neutron star magnetic fields, Atomic data, B-splines, Hartree-Fock-Roothaan.
PACS: 31.15.xr, 32.60.+i, 95.30.Ky, 97.60.Jd..
Classification: 2.1.

External routines: MPI/GFortran, LAPACK, BLAS, FMlib (included in the package).

Does the new version supersede the previous version?: Yes

Nature of problem:
Quantitative modellings of features observed in the X-ray spectra of isolated magnetic neutron stars are hampered by the lack of sufficiently large and accurate databases for atoms and ions up to the last fusion product, iron, at strong magnetic field strengths. Our code is intended to provide a powerful tool for calculating energies and oscillator strengths of medium-Z atoms and ions at neutron star magnetic field strengths with sufficient accuracy in a routine way to create such databases.

Solution method:
The Slater determinants of the atomic wave functions are constructed from single-particle orbitals ψi which are products of a wave function in the z direction (the direction of the magnetic field) and an expansion of the wave function perpendicular to the direction of the magnetic field in terms of Landau states, ψi(ρ,φ,z) = Pi(zNLn=0tinΦni(ρ,φ). The tin are expansion coefficients, and the expansion is cut off at some maximum Landau level quantum number n = NL. In the previous version of the code only the lowest Landau level was included (NL = 0), in the new version NL can take values of up to 7. As in the previous version of the code, the longitudinal wave functions are expanded in terms of sixth-order B-splines on finite elements on the z axis, with a combination of equidistant and quadratically widening element borders. Both the B-spline expansion coefficients and the Landau weights tin of all orbitals have to be determined in a doubly self-consistent way: For a given set of Landau weights tin, the system of linear equations for the B-spline expansion coefficients, which is equivalent to the Hartree-Fock equations for the longitudinal wave functions, is solved numerically. In the second step, for frozen B-spline coefficients new Landau weights are determined by minimizing the total energy with respect to the Landau expansion coefficients. Both steps require solving non-linear eigenvalue problems of Roothaan type. The procedure is repeated until convergence of both the B-spline coefficients and the Landau weights is achieved.

Reasons for new version:
The description of states with partial spin polarisation, which are relevant in the regime of low to intermediate magnetic field strengths βZ <≈ 1, was not included in the version published previously but is vital to gain access to these regimes of the magnetic field strength.

Summary of revisions:
In this new version, we included the electron spin orientation, enhanced the convergence behaviour, reduced the output, sped up the program and built a new result file type, which offers a greater flexibility and reduces file sizes.

Restrictions:
Intense magnetic field strengths are required, since the expansion of the transverse single-particle wave functions using 8 Landau levels will no longer produce accurate results if the scaled magnetic field strength parameter βZ = B/BZ becomes much smaller than unity.

Unusual features:
A huge program speed-up is achieved by making use of pre-calculated binary files. These can be calculated with additional programs provided with this package.

Running time:
1-30 minutes