(Color online) (a) Proposed orientation of AuS unit cell (black box). (b) Atomic structure of . Numerical subscripts denote the coordination of each atom and letter subscripts indicate inequivalent atoms of the same coordination. The cross and circle in (a) (˟ and 엯, respectively) are relevant to structure described in the text.
(Color online) Fully relaxed structures and unit cells (red boxes) for isolated, (a) neutral and (b) charged AuS layers. The structure in (b) has a charge of per cell.
(Color online) (a) Constant height STM images collected at room temperature, (b) STM simulations. Orange and black circles mark lateral positions of Au and S atoms, respectively. The numbers indicate sample bias voltages in mV, and the scan direction is given by .
(Color online) Atom-projected DOS (summed over orbitals) for structure . refers to the Fermi level of isolated layer .
(Color online) Charge density difference plot. The charge density difference between structure and the superposition of atomic densities plotted in the plane of the structure; the scale runs from (black) to (white).
(Color online) Atomic orbitals in structure . AOs for (a) , (b) [similar to ], and (c) ; (d) AOs; [(e) and (f)] AOs for (similar to other S atoms). Red and green surfaces represent positive and negative contour surfaces of the same absolute value.
(Color online) Bonding orbitals in structure . (a) , (b) [similar to and ], and (c) . Symbols are the same as in Fig. 5.
(Color online) Bonding orbitals in structure . in (a) top and (b) side views (similar for other Au–S bonds), and in (c) top and (d) side views. Symbols are the same as in Fig. 5. The isocontour value in (c) is half that in (a), (b), and (d).
Geometric features in structure , in the fully relaxed neutral and charged layers, and in experiment. and denote, respectively, the lattice dimensions (in Å) in the and directions and the angle between lattice vectors for the AuS unit cell. The remaining rows tabulate bond lengths (in Å) in the respective AuS models and in experiment. The experimental bond lengths are taken from the literature of known compounds that contain Au–S or Au–Au bonds with the same formal oxidation states as given in parentheses in the first column. Specifically, the bond length for is taken from crystal data on bulk (Ref. 16). In compounds with bonds, typical bond lengths are if S bridges two atoms and otherwise (Ref. 17). The bond length is about for covalent bonds and for weaker aurophilic interactions (Ref. 17).
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