“…However, there are alternative methods to indirectly characterize OVs by examining the changes they bring in the structure or electronic state, as the production of OVs can alter the electronic configuration and coordination of the surrounding metals, which can serve as a unique identifier for the OVs in metal oxides. 77,87 For instance, the STM (scanning tunneling microscope) can be used to visualize the OV caves, 88,89 while PAS (positron annihilation spectroscopy) can be used to monitor them. 90,91 Moreover, the XRD, ND (neutron diffraction), and XAS (X-ray absorption spectroscopy) techniques can detect changes in the crystalline structure caused by OVs.…”