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[Licence| Download | New Version Template] aenp_v2_0.tar.gz(1136 Kbytes)
Manuscript Title: The DEPOSIT computer code based on the low rank approximations.
Authors: Mikhail S. Litsarev, Ivan V. Oseledets
Program title: DEPOSIT 2014
Catalogue identifier: AENP_v2_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 185(2014)2801
Programming language: C++, Fortran.
Computer: Any computer that can run C++ and Fortran compilers.
Operating system: Any operating system with installed compilers mentioned above. Tested on Mac OS X 10.9 and Ubuntu 12.04.
Has the code been vectorised or parallelized?: Due to the fast computation in the current implementation only a single-threaded version has been developed.
Keywords: Low-rank approximation, 2D cross, Separated representation, Exponential sums, 3D Integration, Slater wave function, Ion-atom collisions, Electron loss, Deposited energy.
PACS: 34.50.Fa, 34.50.Bw, 02.60.Gf, 02.60.Jh.
Classification: 2.6, 4.10, 4.11, 19.1.

External routines: BLAS, LAPACK and ALGLIB. The last one is included in the distribution.

Does the new version supersede the previous version?: Yes

Nature of problem:
For a given impact parameter b to calculate the deposited energy T(b) as a 3D integral over a coordinate space, and ionization probabilities Pm(b). For a given energy of the projectile to calculate the total and m-fold electron-loss cross sections using T(b) values on the whole b-mesh.

Solution method:
Calculation of the 3D-integral T(b) in all points of the b-mesh based on the low rank separated representations of matrices and tensors. For details, please see ref. [1]

Reasons for new version:
The computation of the deposited energy T(b) integral is the slowest part of the program and should be done as fast as possible. To accelerate the program a new approach based on the low rank approximations was applied. It made computational scheme more stable and decreased the computational time by a factor of ~ 103. By means of this approach a bug in the integration routines was found and fixed for a special case of the energy gain.

Summary of revisions:
A two dimensional cross decomposition algorithm was developed as an independent module and was integrated with the energy gain ΔE. For the Slater density ρ(r) a separated representation via a sum of Gaussians was implemented. The calculation of three dimensional integrals T(b) was totally rewritten by using quadrature schemes based on the cross decomposition for energy gain and separated representations for Slater density. Details are reported in ref. [1].

Running time:
For a given energy the total and m-fold cross sections are calculated within about several minutes on a single-core.

[1] M.S. Litsarev, I.V. Oseledets. Fast computation of the deposited energy integrals with the low-rank approximation technique, Computational Science and Discovery 2014 (submitted); arXiv:1403.4068.