Problem 1005

Summary: Erroneous results when materials are defined with zero fraction elements
Product: Geant4 Reporter: Richard Taschereau <perarduaca>
Component: processes/electromagnetic/lowenergyAssignee: Sebastien Incerti <incerti>
Status: RESOLVED FIXED    
Severity: normal CC: Gabriele.Cosmo, perarduaca, Vladimir.Ivantchenko
Priority: P5    
Version: 8.1   
Hardware: PC   
OS: Linux   
URL: http://geant4-hn.slac.stanford.edu:5090/HyperNews/public/get/materials/77.html

Description Richard Taschereau 2008-03-07 19:38:07 CET 
When a material definition contains one or more element with a fraction of zero, the definition is accepted by GEANT4 (no error, no warning); however simulation results are erroneous.  We are reporting this problem now (as the Gate collaboration) but it was initially mentioned in 2006 in the hypernews (see URL above).  

The problem is reported using low-energy processes; it is unknown at this time if other processes are also involved.

Whether a zero fraction should be allowed in a material definition is debatable.  If it is not, then an error message should be issued; if it is, then of course valid results should follow.
Comment 1 Marc.Verderi 2009-01-22 17:14:14 CET 
Old problem. I remember at the time it was submitted that the situation was uneasy in the LowE group.
After discussion with Vladimir and Michel, it looked to be a problem in the LowE package (suspicion was kind of division by the element fraction, regardless this fraction could be zero). This is my recollection of the situation.
Comment 2 Sebastien Incerti 2009-09-25 09:21:01 CEST 
Problem fixed thanks to the new design of low energy classes