6 research outputs found
Dynamical instability and Fermi surface topology in Ni\u3csub\u3e2\u3c/sub\u3eFeGa from first principles
The phonon spectrum of stoichiometric Heusler alloy Ni2FeGa is calculated for the high-temperature cubic austenite phase by using first-principles density functional perturbation theory. We also compute the elastic constants of the alloy from the initial slopes of the acoustic phonon branch. The TA2 phonon branch along [110] direction shows softening with a minimum dip at ζ=0.58 which indicates the possibility of modulated phases prior to martensitic transformation. We also map the Fermi surface of this alloy both in 3D and 2D to check the presence of any nesting vectors. The observed nesting parameter is in good agreement with the above value of the wave vector in the [110] direction where phonon softening occurs
Atomic level understanding of site-specific interactions in Polyaniline/TiO2 composite
The results of spin-polarized density functional theory calculations find
that band gap engineering can be achieved by site-specific interactions in a
composite consisting of polyaniline and TiO2 nanoparticles. Interactions in the
composite matrix are found to be mediated by Ti atoms inducing dependency of
location of the conduction band minimum on the polyaniline site which is being
probed by TiO2. This dependency is due to subtle changes in the nature of
valance or conduction states near Fermi level introduced by the interacting
matrix sites. The results therefore suggest that optimization of the synthesis
parameters at atomic level can be an effective way to improve performance of a
photovoltaic device based on PAni- TiO2 composite