2,746 research outputs found
Structural Phase Stability in Fluorinated Calcium Hydride
In order to improve the hydrogen storage properties of calcium hydride
(CaH2), we have tuned its thermodynamical properties through fluorination.
Using ab-initio total energy calculations based on density functional theory,
the structural stability, electronic structure and chemical bonding of CaH2-xFx
systems are investigated. The phase transition of fluorinated systems from
orthorhombic to cubic structure has been observed at 18% fluorine doped CaH2.
The phase stability analysis shows that CaH2-xFx systems are highly stable and
the stability is directly correlating with their ionicity. Density of states
(DOS) plot reveals that CaH2-xFx systems are insulators. Partial DOS and charge
density analyses conclude that these systems are governed by ionic bonding. Our
results show that H closer to F can be removed more easily than that far away
from F and this is due to disproportionation induced in the bonding interaction
by fluorination
Phosphorene-AsP Heterostructure as a Potential Excitonic Solar Cell Material - A First Principles Study
Solar energy conversion to produce electricity using photovoltaics is an
emerging area in alternative energy research. Herein, we report on the basis of
density functional calculations, phosphorene/AsP heterostructure could be a
promising material for excitonic solar cells (XSCs). Our HSE06 functional
calculations show that the band gap of both phosphorene and AsP fall exactly
into the optimum value range according to XSCs requirement. The calculated
effective mass of electrons and holes show anisotropic in nature with effective
masses along -X direction is lower than the -Y direction
and hence the charge transport will be faster along -X direction. The
wide energy range of light absorption confirms the potential use of these
materials for solar cell applications. Interestingly, phosphorene and AsP
monolayer forms a type-II band alignment which will enhance the separation of
photogenerated charge carriers and hence the recombination rate will be lower
which can further improve its photo-conversion efficiency if one use it in
XSCs
Ti4+ Substituted Magnesium Hydride as Promising Material for Hydrogen Storage and Photovoltaic Applications
In order to overcome the disadvantages of MgH2 towards its applications in
on-board hydrogen storage, first principle calculations have been performed for
Ti (2+, 3+, and 4+) substituted MgH2. Our calculated enthalpy of formation and
H site energy implies that Ti substitution in Mg site reduces the stability of
MgH2 which improve the hydrogen storage properties and Ti prefers to be in +4
oxidation state in MgH2. The bonding analyses through partial density of
states, electron localization function and Bader charge of these systems
confirm the existence of iono-covalent bonding. Electronic structure obtained
from hybrid functional calculations show that intermediate bands (IB) are
formed in Ti4+ substituted MgH2 which could improve the solar cell efficiencies
due to multiple photon absorption from valence band to conduction band via IBs
and converts low energy photons in the solar spectrum also into electricity.
Further, our calculated carrier effective masses and optical absorption spectra
show that Ti4+ substituted MgH2 is suitable for higher efficiency photovoltaic
applications. Our results suggest that Ti4+ substituted MgH2 can be considered
as a promising material for hydrogen storage as well as photovoltaic
applications
Statistical and metallographic aspects of fatigue failure mechanisms in metals
Statistical analysis and metallographic aspects of fatigue failure mechanisms in copper alloy
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