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Phonon Drag and Carrier Diffusion Contributions in Thermoelectric Power of M_3C_{60} (M = K, Rb) Fullerides

100%

Varshney D., Singh N.

Acta Physica Polonica A

2013

vol. 123

issue 4

752-760

The thermoelectric power (S) of M_3C_{60} (M = K, Rb) alkali intercalated fullerides is theoretically investigated by considering the Mott expression within parabolic band approximation to reveal the electron diffusive thermoelectric power (S_{c}^{diff}). We follow the Fermi energy as electron parameter and S_{c}^{diff} discerned linear temperature dependence. S infers a change in slope above transition temperature and becomes almost linear above 70 K for M_3C_{60} alkali intercalated fullerides. As a next step, the phonon drag thermoelectric power (S_{ph}^{drag}) is computed within relaxation time approximation when thermoelectric power is limited by scattering of phonons from defects, grain boundaries, phonons and electrons as carriers. It is noticed that the S_{ph}^{drag} of K_3C_{60} is anomalous and it is an artifact of strong phonon-electron and -phonon scattering mechanism. The thermoelectric power within relaxation time approximation has been taken into account ignoring a possible energy dependence of the scattering rates. Behaviour of S(T) is determined by competition among the several operating scattering mechanisms for the heat carriers and a balance between carrier diffusion and phonon drag contributions in M_3C_{60} (M = K, Rb) alkali intercalated fullerides.

First-Principles Calculations of Structural, Electronic, Optical, and Thermodynamic Properties of CdS, CdTe and Their Ternary Alloys CdS_{1-x}Te_{x} (0.0 ≤ x ≤1.0)

61%

Ameri M., Mesbah S., Al-Douri Y., Bouhafs B., Varshney D., Ameri I.

Acta Physica Polonica A

2014

vol. 125

issue 5

1110-1117

Using first-principle method, we investigate the structural, electronic, optical, and thermodynamic properties of the CdS_{1-x}Te_x semiconductor alloys using generalized gradient approximation for the exchange-correlation potential calculation. The ground state properties are determined for the bulk materials (CdS and CdTe) in cubic phase. Quantities such as the lattice constants and bulk modulus of interest are calculated. Detailed comparisons are made with published experimental and theoretical data and show generally good agreement. The calculated lattice constants scale linearly with composition (Vegard's law). The microscopic origins of the bowing parameter were explained using the contributions from volume deformation, charge transfer and structural relaxation approach. The refractive index and optical dielectric constant for the alloys of interest were calculated by using different models. In addition, the thermodynamic stability of the alloys was investigated by calculating the critical temperatures of alloys.

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2 Acta Physica Polonica A

1 2014

1 2013

2 Varshney D.

1 Al-Douri Y.

1 Ameri I.

1 Ameri M.

1 Bouhafs B.

1 Mesbah S.

1 Singh N.

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Phonon Drag and Carrier Diffusion Contributions in Thermoelectric Power of M_3C_{60} (M = K, Rb) Fullerides

First-Principles Calculations of Structural, Electronic, Optical, and Thermodynamic Properties of CdS, CdTe and Their Ternary Alloys CdS_{1-x}Te_{x} (0.0 ≤ x ≤1.0)