Supporting Information - Can NbO keep nbo topology under electrons? –Unveiling novel aspects of Niobium monoxide at the atomic scale

The experimental PXRD data of the pristine NbO is showed in Figure S1 and Table S1. The diffraction peaks were indexed assuming Pm-3m space group with unit cell parameter a = b = c = 4.211 Å. The measured intensities in Table S1 were integrated without background.Elemental analysis of the pristine NbO was performed by EDS. Figure S2 is the elemental mapping and EDS results of a pristine NbO crystal. A statistical elemental experiment was performed on 20 different pristine NbO crystals, showed in Table S2. Elemental analysis of both the pristine NbO and fully transformed NbO were measured by EELS, showed in Figure S3-S4. The experiment results indicated that both the pristine and transformed NbO have an elemental composition ratio of Nb:O = 1:1.Table S3-S7 and Figure S5-S7 are the crystal structure result of the pristine NbO solved by SCXRD. The atoms occupancy at different sites were refined against the SCXRD and also PXRD data (Table S8).The Cs-corrected HAADF-STEM images of NbO were obtained along three main zone axes under electron dose control, showed in Figure S8-S10. All the raw images were performed by plane group average and the intensities of atom columns were measured to see the intensity change.The intensities of the columns measured from the three zone axes are showed in Figure S13. It was proposed that the structure transformation follows the evolution from VaNb = 1, VcNb = 0 to the final stage VaNb = VcNb = 0.25.EELS data collected from the area of the pristine and transformed NbO in one crystal are showed in Figure S18.Figure S19 shows the outlook and the morphology of NbO crystal. The cleavage was indexed as {110} and {100} crystal plane, see Figure S20.Figure S21 shows a wide area of the pristine NbO viewed along [100] direction. this crystal area contains an aggregation of the antiphase boundary planar defects, and the cleavage edges are also observed. At the center of this image is an local area suffered from electron beam irradiated transformation.The model of planar dislocation was employed to calculate the total energy difference, see Figure S22.Peer reviewe