The bonding Wannier functions ͑WF's͒ associated with the O 2s/2p valence states of TiO 2 have been calculated for both the rutile and the anatase forms. They are similar in the two polymorphs, and correspond to three distorted O sp 2 -like hybrids in the plane of the Ti 3 coordination triangle, and one p-like orbital perpendicular to this plane. For both structures, the WF's show that the OTi 3 triangular complex is the relevant structural unit for understanding TiO 2 electronic properties. WF's differences between the two phases are quantitatively measured with a multipole expansion of the static charge density of the fourfold WF complex. These differences reflect the opposite distortion from equilateral shape that the isosceles Ti 3 triangle has in the two structures, and correlate quantitatively with the opposite anisotropy of the dynamical Born charge tensors calculated for the two polytypes.
The origin of electronic states localized at ZnSe/Ge (110) interface is investigated by means of ab initio pseudopotential calculations. Some selected interface configurations are considered, one corresponding to the abrupt interface and others corresponding to partially disordered interfaces, with Zn-Ge or Se-Ge swaps. Remarkably, the existence of interface electronic states within the heterojunction band gap critically depends on the atomic-scale morphology of the interface: unlike the abrupt case, disordered interfaces exhibit localized states extending over the whole interface Brillouin zone. The presence of interfacial density of states, experimentally detectable, is therefore an indication of disorder and atomic interdiffusion.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.