def SetDefaultSubstances():
    """Fills in default items for the SASD Substances dictionary"""
    return {'Substances': {'vacuum': {'Elements': {}, 'Volume': 1.0,
        'Density': 0.0, 'Scatt density': 0.0, 'XImag density': 0.0},
        'unit scatter': {'Elements': None, 'Volume': None, 'Density': None,
        'Scatt density': 1.0, 'XImag density': 1.0}}}
