Python implementation of A. Sierk's BARFIT

Read online version: https://gitlab.in2p3.fr/gregoire.henning/fisbar-python/-/blob/master/README.md

History

Between 1984 and 2986, A. J. Sierk developped the BARFIT (also refered as fisbar) routine to compute fission barrier, ground state energy and maximum angular momentum a nucleus can sustain in the framework of the liquid drop model.

The routine used fitted value over a wide range of A, Z and L. In fact, it is an impressive piece of code that performs a global fit, where we would use today some kind of machine learning model. The full calculation and routine is described in A. Sierk, Phys. Rev. C33 (1986) 2039..

The routine is still available today from the RIPL-3 website (Readme of original routine).

Python implementation

The 1986 Fortran routine is old and may not compile on modern computers. However, the routine is still of great interest, as it is able to provide an estimate for a fission barrier for light elements (For heavy ones, one can find the predicted values by P. Moeller, A. J. Sierk, et al : "HEAVY-ELEMENT FISSION BARRIERS").

The code of is quite straightforward, so it's not too hard to translate it into python.

This is one implementation in python 3.6. The code is almost a line-for-line translation of the original fortran routine. As is, it is quite un-pythonic, but it makes the working, testing and checking easier when writing from the orginal code.

The lpoly routine of Sierk was replaced with the numpy.polynomial.legendre module to obtain the legendre polynomial values. (This is the only external dependency of the module).

Accuracy

The output of the code is compared to the references values given by A. Sierk in the original Fortran file. The python module was tested against theses values :

			A. Sierk's reference values			Python Implementation results
Z	A	L	B_f	Egs	Lmax	Bf	Egs	Lmax
28	58	0	33.14	0.0	46.1	33.14	0.00	46.13
28	58	25	19.5	21.36	46.1	18.52	20.00	46.13
28	58	40	2.97	49.66	46.1	2.47	31.18	46.13
28	58	46.1	0	59.14	46.1	0.00	58.56	46.13
65	153	0	28.88	0.0	82.3	28.88	0.00	82.27
65	153	50	16.16	19.0	82.3	14.16	19.80	82.27
65	153	80	0.26	45.24	82.3	0.12	31.47	82.27
65	153	82.3	0.0	47.01	82.3	0.00	47.29	82.27
93	229	0	3.76	0.0	68.1	3.76	0.00	68.13
93	229	45	1.26	8.21	68.1	1.22	9.12	68.13
93	229	68.1	0.0	17.96	68.1	0.00	17.83	68.13

⚠ We notice significant differences. This is probably due to floating point precision between today's python and the Fortran used by A. Sierk to perform the fits in 1986. Therefore, the values should be not be taken at face value, but they are a good first approximation.

Online version

An online notebook has been created to allow the execution of the code online. via binder.

Running Locally

You can also install and run the routine on your local computer

Installation

Via pip

The prefered way of installing the library is via pip by running the following command:

$ pip install fisbar

via setup.py

Installation can be perfomed using the dist/fisbar-20201120.tar.gz archive, that contain the module installation files, to be installed via :

$ python setup.py

Running

As a standalone program

Usage:

$ python -m fisbar [-h] [--style {columns,human,dict,yaml}] Z A [L]

This runs the module at stand alone program.

Arguments are Z, A (both mandatory), L (default = 0) and output style.

The style can be columns, human, dict (default) or yaml. When using columns output style, the results are outputed as columns following : Z A L bfis Egs Lmax. human outputs the results in a readable format. yaml as a Yaml formated dictionnary and dict as a python dictionnary (also compatible with json). When a value is not computed (because the code failed), it appears either as 0 or ***.

As a python module

The fisbar routine can be used in a python code by importing it inside your program. For example

import fisbar

Z = 92
A = 238
L = 0

print(fisbar,fisbar(Z, A, L))

will output

{}

example

Versions

• Current:

Authors

• Greg Henning

Licence

• CeCILL FREE SOFTWARE LICENSE AGREEMENT
• Original file license :

Copyright, 1986,  The Regents of the University of California.
This software was produced under a U. S. Government contract
(W-7405-ENG-36) by the Los Alamos National Laboratory, which is
operated by the University of California for the U. S. Department
of Energy.  The U. S. Government is licensed to use, reproduce,
and distribute this software.  Permission is granted to the public
to copy and use this software without charge, provided that this
notice and any statement of authorship are reproduced on all
copies.  Neither the Government nor the University makes any
warranty, expressed or implied, or assumes any liability
or responsibility for the use of this software.