190 research outputs found
Pseudo-half-metalicity in the double perovskite SrCrReO from density-functional calculations
The electronic structure of the spintronic material SrCrReO is
studied by means of full-potential linear muffin-tin orbital method. Scalar
relativistic calculations predict SrCrReO to be half-metallic with a
magnetic moment of 1 . When spin-orbit coupling is included, the
half-metallic gap closes into a pseudo-gap, and an unquenched rhenium orbital
moment appears, resulting in a significant increase of the total magnetic
moment to 1.28 . This moment is significantly larger than the
experimental moment of 0.9 . A possible explanation of this discrepancy
is that the anti-site disorder in SrCrReO is significantly larger than
hitherto assumed.Comment: 3 Pages, 1 figure, 1 Tabl
Phase Stability and Thermoelectric Properties of the Mineral FeS2: An Ab Initio Study
First principles calculations were carried out to study the phase stability
and thermoelectric properties of the naturally occurring marcasite phase of
FeS at ambient condition as well as under pressure. Two distinct density
functional approaches has been used to investigate the above mentioned
properties. The plane wave pseudopotential approach was used to study the phase
stability and structural, elastic, and vibrational properties. The full
potential linear augment plane wave method has been used to study the
electronic structure and thermoelectric properties. From the total energy
calculations, it is clearly seen that marcasite FeS is stable at ambient
conditions, and it undergoes a first order phase transition to pyrite FeS
at around 3.7 GPa with a volume collapse of about 3. The calculated ground
state properties such as lattice parameters, bond lengths and bulk modulus of
marcasite FeS agree quite well with the experiment. Apart from the above
studies, phonon dispersion curves unambiguously indicate that marcasite phase
is stable under ambient conditions. Further, we do not observe any phonon
softening across the marcasite to pyrite transition and the possible reason
driving the transition is also analyzed in the present study, which has not
been attempted earlier. In addition, we have also calculated the electronic
structure and thermoelectric properties of the both marcasite and pyrite
FeS. We find a high thermopower for both the phases, especially with p-type
doping, which enables us to predict that FeS might find promising
applications as good thermoelectric materials.Comment: 10 Figure
Thermoelectric properties of zinc based pnictide semiconductors
We report a detailed first principles density functional calculations to understand the electronic
structure and transport properties of Zn-based pnictides ZnXPn
2
(X: Si, Ge, and Sn; Pn: P and As)
and ZnSiSb
2
. The electronic properties calculated using Tran-Blaha modified Becke-Johnson func-
tional reveals the semi-conducting nature, and the resulting band gaps are in good agreement with
experimental and other theoretical reports. We find a mixture of heavy and light bands in the band
structure which is an advantage for good thermoelectric (TE) properties. The calculated transport
properties unveils the favour p-type conduction in ZnXP
2
(X: Si, Ge, and Sn) and n-type conduc-
tion in ZnGeP
2
and ZnSiAs
2
. Comparison of transport properties of Zn-based pnictides with the
prototype chalcopyrite thermoelectric materials implies that the thermopower values of the investi-
gated compounds to be higher when compared with the prototype chalcopyrite thermoelectric
materials, together with the comparable values for electrical conductivity scaled by relaxation time.
In addition to this, Zn-based pnictides are found to possess higher thermopower than well known
traditional TE materials at room temperature and above which motivates further research in these
compounds
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