GEF 2016/1.2

Important notice: By verifying the results of GEF 2016/1.1 at higher initial excitation energies (above 10 MeV), a systematic overestimation of the fragment excitation energies (TXE) was observed. The reason was a too strong energy dependence of the shape fluctuations at scission. This problem should be solved in the version 2016/1.2.
This problem does not exist for the Stand-alone version (GEFSUB). That means that the subroutines of versions 2016/1.1 and 2016/1.2 are identical and correspond to the stand-alone version GEF 2016/1.2.

An extended version of GEF-2016/1.2 that includes delayed processes (output of delayed-neutron multiplicities, delayed-neutron emitters, cumulative fission-fragment yields in ENDF format) is available on demand. It provides also an option for producing random files of fission-fragment yields in ENDF format.

We are happy about any feed-back (mail to schmidt-erzhausen<at> This helps to correct errors, to improve the quality of the model and to better respond to the needs and preferences of the users.

Use of the GEF code is subject to the GNU GENERAL PUBLIC LICENSE agreement that you find here: <License>.

Stand-alone version (Monte-Carlo method)

The stand-alone version of the GEF code is written in FreeBASIC (a). The FreeBASIC compiler produces binary code from the same source on Windows (b) and on Linux. The executable uses the C library.  For  the Windows version, a GUI is provided, written in JustBasic (c). The Windows version runs also on Linux with Wine (d).  The Windows version runs also on OS X (e) with Wine (d).

a) FreeBASIC is available from with no cost.
b) Windows is either a registered trademark or a trademark of Microsoft Corporation in the United States and/or other countries.
c) JustBasic is available from with no cost.
d) Wine is a windows compatibility layer for Linux and Mac OS X (
e) OS X is a trademark of Apple Inc., registered in the U.S. and other countries.

Quick start on Windows:

Quick start on Linux:

Windows version

Input mask of the graphical user interface:

Input maks of GEF GUI

For Windows and Linux

Complete package

Updated version of the complete package (2. 5. 2018). (Extended input and output options and some technical corrections. The physics is not changed.)

Updated special version of the complete package (9. 8. 2018). (Like the updated version; in addition, the shell effect in the symmetric fission valley is washed out with increasing excitation energy.)


Readme file (Technical information, list of relevant publications)
JEFF-Report 24, part I (Comprehensive documentation of the GEF model.)
JEFF-Report 24, part II (Technical information on the GEF code.)

Source (for Windows and Linux)

Source files


Input files for extended input options
Distribution of entrance energies (example)
List of input parameters (example)
See Readme file for more detailed information.
Data tables in XML format (example)
List-mode file (example)   (short sample of most complete event list)
Raw data for the multi-variate distribution of fission-fragment yields from calculations with perturbed parameters (example)
See Readme file for more detailed information.

You may consider using the Windows version of GEF on Linux with Wine in order to profit from the more comfortable input handling offered by the graphical user interface. This option may also solve problems of missing libraries under Linux.

Subroutine (Folding method) 

The subroutine aims for being used in combination with other nuclear-reaction codes. For a given fissioning nucleus with excitation energy E* and angular momentum I it calculates complete distributions of a number of fission observables before emission of prompt neutrons and prompt gamma radiation with the GEF model.

Notice to the users of the subroutine version of GEF:
The subroutine GEFSUB 2016/V1.2 is identical to the subroutine GEFSUB 2016/V1.1. (See notice above.) Thus, there is no need for updating from GEFSUB 2016/V1.1 to GEFSUB 2016/V1.2. The packages below are only provided for practical reasons.


Technical description of the subroutine

FreeBASIC version

Source files

FORTRAN version

Source files