χ⁽²⁾ and χ⁽³⁾ at charged interfaces in SFG spectroscopy are distinctively calculated using MD simulations.

Vibrational sum frequency generation (VSFG) spectroscopy is a widely used probe of interfaces and, having ideal surface sensitivity and selectivity, is particularly powerful when applied to wet and soft interfaces. Although VSFG spectroscopy can sensitively detect molecular details of interfaces, interpretation of observed spectra has, until recently, been challenging and often ambiguous. The situation has been greatly improved by remarkable advances in computational VSFG analysis on the basis of molecular modeling and molecular dynamics simulation. This article reviews the basic idea of computational VSFG analysis and recent applications to both aqueous and organic interfaces.

Photochemical reactions at the air–water interface can show remarkably different rates from those in bulk water. The present study elucidates the reaction mechanism of phenol characteristic at the air–water interface by the combination of molecular dynamics simulation and quantum chemical calculations of the excited states. We found that incomplete hydrogen bonding to phenol at the air–water interface affects excited states associated with the conical intersection and significantly reduces the reaction barrier, resulting in the distinctively facilitated rate in comparison with the bulk phase. The present study indicates that the reaction dynamics can be substantially different at the interfaces in general, reflecting the difference in the stabilization energy of the electronic states in markedly different solvation at the interface.