Quadrupole susceptibility automatic calculator in sum frequency generation spectroscopy incorporating magnetic contributions and refined local fields

While sum frequency generation (SFG) spectroscopy is known to have acute interface selectivity owing to the dipole approximation, it has been a long-standing concern to understand the contribution of higher-order polarizations and/or bulk. Motivated by recent advances in microscopic theory of SFG including quadrupole, this work reports our recent development of the calculation tool of quadrupole susceptibility, namely, QSAC. QSAC aims at evaluating relative intensity of surface/bulk and dipole/q