Comment on "Sum-frequency vibrational spectroscopy of centrosymmetric molecule at interfaces" [J. Chem. Phys. 158, 074701 (2023)].

The article discusses the debate surrounding the mechanism of sum frequency generation (SFG) signals emitted by liquid benzene. The authors argue that the main signal comes from local modes generated by symmetry breaking, while another paper challenges this view and suggests that the dominant mechanism is the interfacial electric quadrupole. The authors refute this argument, stating that their previous paper considered both symmetry breaking and the electric quadrupole in their calculations, while the opposing paper did not properly examine the effect of symmetry breaking. The authors present evidence of symmetry breaking through computational evaluations and the reversal of symmetry breaking at the silica-benzene interface. They recommend that the opposing authors consider these evidences before drawing their conclusion. [Extracted from the article]