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Manuscript Title: The TDHF Code Sky3D
Authors: J. A. Maruhn, P.-G. Reinhard, P. D. Stevenson, A. S. Umar
Program title: Sky3D
Catalogue identifier: AESW_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 185(2014)2195
Programming language: Fortran 90. The OpenMP version requires a relatively recent compiler; it was found to work using gfortran 4.6.2 or later and the Intel compiler version 12 or later.
Computer: All computers with a Fortran compiler supporting at least Fortran 90.
Operating system: All operating systems with such a compiler. Some of the Makefiles and scripts depend on a Unix-like system and need modification under Windows.
Has the code been vectorised or parallelized?: Yes, Runs under OpenMP and MPI, unlimited number of processors can be used.
Keywords: Nuclear theory, Mean-field models, Nuclear reactions.
Classification: 17.16, 17.22, 17.23.

External routines: LAPACK, FFTW3

Nature of problem:
The time-dependent Hartree-Fock equations can be used to simulate nuclear vibrations and collisions between nuclei for low energies. This code implements the equations based on a Skyrme energy functional and also allows the determination of the ground-state structure of nuclei through the static version of the equations. For the case of vibrations the principal aim is to calculate the excitation spectra by Fourier-analyzing the time dependence of suitable observables. In collisions, the formation of a neck between nuclei, the dissipation of energy from collective motion, processes like charge transfer and the approach to fusion are of principal interest.

Solution method:
The nucleonic wave function spinors are represented on a three-dimensional Cartesian mesh with no further symmetry restrictions. The boundary conditions are always periodic for the wave functions, while the Coulomb potential can also be calculated for an isolated charge distribution. All spatial derivatives are evaluated using the finite Fourier transform method. The code solves the static Hartree-Fock equations with a damped gradient iteration method and the time-dependent Hartree-Fock equations with an expansion of the time-development operator. Any number of initial nuclei can be placed into the mesh in with arbitrary positions and initial velocities.

The reliability of the mean-field approximation is limited by the absence of hard nucleon-nucleon collisions. This limits the scope of applications to collision energies about a few MeV per nucleon above the Coulomb barrier and to relatively short interaction times. Similarly, some of the missing time-odd terms in the implementation of the Skyrme interaction may restrict the applications to even-even nuclei.

Unusual features:
The possibility of periodic boundary conditions and the highly flexible initialization make the code also suitable for astrophysical nuclear-matter applications.

Additional comments:
This is an Open Access program

Running time:
The running time depends strongly on the size of the grid, the number of nucleons, and the duration of the collision. For a single-processor PC-type computer it can vary between a few minutes and weeks.