fake_mat     1.100000E+00    2
h:1     5.000000E+01    1
k:39     5.000000E+01    19

water     1.200000E+00    2
h:1     9.090909E+00    1
o:16     9.090909E+01    8

helium     1.300000E+00    1
he:4     1.000000E+02    2

# void material
mat_void 0.0 1
he 1 2
