Investigation of the van der Waals epitaxy gap in isostructural semiconducting germanium tellurides: HfGeTe4 and ZrGeTe4

Two isostructural semiconducting germanium tellurides: HfGeTe4 and ZrGeTe4 have been investigated for the van der Waals epitaxy gap existing between layers of atoms using the charge density route. The Maximum Entropy Method (MEM) is used for the reconstruction of the charge density derived from the XRD information. 3-dimensional charge density maps visualize the van der Waals epitaxy gap, while 2-dimensional and 1-dimensional charge density maps and profiles have been picturised and quantified for the localized charges between the atoms, especially in the valence region. The types of bonding existing are identified, and the strength of the bonds is quantified in order to identify the weak van der Waals and strong covalent, metallic bonds which exist in the chosen systems. The charge density and van der Waals epitaxy gap in both systems reveal the fact that HfGeTe4 is more fragile than ZrGeTe4.