Skip to main content
. 2021 Aug 6;33(39):2102356. doi: 10.1002/adma.202102356

Figure 6.

Figure 6

Illustration of the bond formation in GeTe and the resulting band structure. Atomic orbitals of Ge and Te responsible for bond formation in GeTe are depicted on the left. σ‐bonds are formed from p‐orbitals, which are occupied by about half an electron pair (ES ≈ 1), resulting in a metallic band (blue curves on the right side of the figure). However, moderate charge transfer and significant electron sharing result in a small bandgap. When alloying GeTe with Se, the degree of electron sharing significantly increases (cf. Figure 1), resulting in an increased Peierls distortion, which can be verified experimentally (cf. Figure 5). Top part on left‐hand side: Adapted with permission.[ 31 ] Copyright 2020, The Authors, published by Wiley‐VCH. On the bottom, from left to right, valence charge density plots for GeTe in the cubic, rhombohedral (equilibrium), and orthorhombic phases. The central atom is Ge. Same color scale ranges and isolines values for all phases. The alignment of the p orbitals and extent of the Peierls distortion is linked to the existence of MVB. In the orthorhombic phase, the loss of orbital alignment and large Peierls distortion ratios in the y‐direction of the figure is triggering the disappearance of MVB. The projection plane is defined by a Ge–Te–Te triplet of atoms (other atoms are thus out of‐plane for the rhombohedral and orthorhombic phases).