$useadditionalaffinity (3D)

$useadditionalaffinity is the same as $affinity is function to assign the affinity of each material for an additional regions. Besides the gmsh's volume, user can define the simple geometric volume shape to assign additional region. Therefore, they will need to assign affinity also if %affinity command is used

For examples:

$useadditionalaffinity
4.05
1.25
2.35 

This means there are three materials in total. the affinity of the first material is 4.05 eV The affinity of the second material is 1.25 eV, and the last one is 2.35 eV.