def METHOD_NAME(A='Ga', B='As'):
    # Lattice constants from Shishkin and Kresse, PRB 75, 235102 (2007)
    assert A in ['Si', 'Ga', 'Cd', 'Zn', 'B', 'Al']
    assert B in ['C', 'As', 'S', 'O', 'N', 'P']
    from ase.lattice import bulk
    if A=='Si' and B=='C':
        ase_atom = bulk('SiC', 'zincblende', a=4.350*A2B)
    elif A=='Ga' and B=='As':
        ase_atom = bulk('GaAs', 'zincblende', a=5.648*A2B)
    elif A=='Ga' and B=='N':
        ase_atom = bulk('GaN', 'zincblende', a=4.520*A2B)
    elif A=='Cd' and B=='S':
        ase_atom = bulk('CdS', 'zincblende', a=5.832*A2B)
    elif A=='Zn' and B=='S':
        ase_atom = bulk('ZnS', 'zincblende', a=5.420*A2B)
    elif A=='Zn' and B=='O':
        ase_atom = bulk('ZnO', 'zincblende', a=4.580*A2B)
    elif A=='B' and B=='N':
        ase_atom = bulk('BN', 'zincblende', a=3.615*A2B)
    elif A=='Al' and B=='P':
        ase_atom = bulk('AlP', 'zincblende', a=5.451*A2B)
    else:
        raise NotImplementedError('No formula found for system %s %s. '
                                  'Choose a different system?  Or add it to the list!' % (A, B))
    return ase_atom