Abstract Understanding the structure of semiconductor–electrolyte interfaces under operating conditions is crucial for designing electrodes in photoelectrochemistry and electrocatalysis. However, only few experimental methods exist that give real‐time access to the very interface. Here, reflection anisotropy spectroscopy (RAS) is an emerging technique in the field of spectroelectrochemistry. We computationally investigate how the surface structure of clean and oxygenated InP(001) surfaces—in vacuum and in contact with water—and its evolution over time affect the optical response. Depending on the electronic structure of the respective surfaces, different species are adsorbed, resulting in changes of the anisotropy clearly visible in the spectroscopic fingerprint, while the presence of stabilizes certain configurations. Distinct fluctuations of the individual spectra are observed during the molecular dynamics trajectory. However, the resulting time‐averaged spectra show a rather good agreement with the respective spectra of the reference structure for most structures. This means that—depending on the surface—the geometry‐optimized structures might be suitable for comparison with experiment or not. This behavior differs from the case of metals and can be attributed to the semiconducting nature of the system. Our findings highlight the need to account for the electrochemical environment in computational RAS.
Yadav et al. (2026) studied this question.