Figure 7.

Theoretical ε₂(ω) as a function of the Peierls Distortion (i.e., R _long/R _short). a) Optical absorption (ε₂(ω)) as a function of the degree of the R _long/R _short ratio for rhombohedral GeTe (green) and orthorhombic GeTe (red), confirming the experimental findings of a discontinuous transition from MVB to CB; b) electronic ground state energy as a function of the R _long/R _short ratio. The optimized orthorhombic phase is anisotropic, with two different Peierls distortion ratios. At comparable cohesive energy, one can find two rhombohedral phases with different volumes (larger triangles). These rhombohedral phases differ by less than 2 meV per atom in energy, but vary by more than 5% in volume, an absorption peak shifted by about 0.2 eV (inset) and a decreased dielectric constant for the larger volume structure. c) A scheme demonstrating the effect of increasing ES on the R _long/R _short ratio and on ε₂(ω). These findings confirm the discontinuous character of the MVB‐CB border.