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Figure 3
Photoinduced orbital reconfiguration and ionic displacements. (a) DFT calculation of electron density distributions for the intact and photoexcited states (10% of valence electrons upshift). Electron-filled states are shown by shaded gray regions. (b) Spatial charge distribution from DFT (see Section S4 the supporting information for details). Bonding electrons are photo-depleted to occupy anti-bonding orbitals weakening the interatomic bonding. (c) Changes in the charge distribution after photoexcitation are emphasized by subtracting the charge distribution of the intact state, which manifests the charge density reduction at the bonding site between Ge ions (green) and increases the anti-bonding sites (magenta). (d) Structure model with the photo-induced ionic displacements in a Ge tetrahedron. Ge ions are displaced along the [111] equivalent direction, breaking the local tetrahedral site symmetry. Ionic displacements are shown via the (001) and (110) plane viewing perspectives, displaying a Ge tetrahedron (gray box) within a conventional unit cell. (e) Atomic structure with the photoinduced ionic displacement with the lower site symmetry of 3m at the 32e position is shown to be consistent with the observed ATS reflection (see Section S3 of the supporting information for details).

IUCrJ
Volume 10| Part 6| November 2023| Pages 700-707
ISSN: 2052-2525
https://doi.org/10.1107/S2052252523007935