In molecular dynamics simulations, OpenMX uses the atomic mass defined in
'Set_Atom_Weight() of SetPara_DFT.c'. However, one can easily change the
atomic mass by the keyword
'Definition.of.Atomic.Species'.
In such a case, the atomic mass is defined by the fourth column as
<Definition.of.Atomic.Species H H5.0-s1 H_PBE19 2.0 C C5.0-s1p1 C_PBE19 12.0 Definition.of.Atomic.Species>