Electronic structure of rare-earth nickel pnictides: Narrow-gap thermoelectric materials

Larson, P.; Mahanti, S. D.; Sportouch, S.; Kanatzidis, Mercouri G.

doi:10.1103/physrevb.59.15660

Cited by 139 publications

(84 citation statements)

References 22 publications

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“…6 Half-Heuslser compounds are semiconductors when there are 18 valence electrons per unit cell. [7][8][9][10][11][12] This is indeed seen in HfCoSb where calculations with local density and generalized gradient approximations (LDA/GGA) give a band gap of ∼1.0 eV at 0 K. Compared to HfCoSb, PbTe has a simple rocksalt structure with 2-interpenetrating FCC lattice. The band structure of PbTe is well-known.…”

Section: Introductionmentioning

confidence: 76%

Validity of the rigid band approximation in the study of the thermopower of narrow band gap semiconductors

2012

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Theoretical studies of thermoelectric properties using ab initio electronic structure calculations help not only to understand existing experimental data but also to predict new materials which can be potentially good thermoelectrics. However, in these studies it is inevitable to employ some approximations. It is therefore important to verify their reliability. To this end, we have investigated the validity of the rigid band approximation (RBA), commonly used in calculating thermopower (S) in doped (sometimes heavily) narrow band gap semiconductors. We have considered two important systems: half-Heusler (HH) HfCoSb and PbTe. We calculate band structures of pure and doped systems (using quasi-periodic approximation-QPA) by employing density-functional method. We then use Boltzmann transport theory to calculate thermopower using both RBA and the band structure with QPA. We find that band structures do not change significantly when isovalent impurities are present excepting in specific cases. However, charged impurities (relevant to the doping case) providing carriers can change the host band structure appreciably. We find that impurities in general remove existing degeneracies which tend to reduce the RBA value of | S |. The reduction is significant in both HfCoSb and PbTe when charged defects are present.

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Section: Introductionmentioning

confidence: 76%

Validity of the rigid band approximation in the study of the thermopower of narrow band gap semiconductors

2012

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“…The treatment of exchange and correlation energy is adopted in the form of Perdew-Burke-Ernzerhof (PBE) [23] with the generalized gradient approximation (GGA). It's necessary to add a Hubbard-type term U [24] to act on the La 5d and Pt 5d states, which can greatly improve the quality of PBE and give the correct electronic structure [25]. We use an effective Hubbard U of 8.1 eV for La and 3.0 eV for Pt, as obtained from the AFLOWLIB.org consortium repository [26].…”

Section: Methodsmentioning

confidence: 99%

LaPtSb: a half-Heusler compound with high thermoelectric performance

Xue

Liu

Fan

et al. 2016

Phys. Chem. Chem. Phys.

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The electronic and transport properties of the half-Heusler compound LaPtSb are investigated by performing first-principles calculations combined with semi-classical Boltzmann theory and deformation potential theory. Compared with many typical half-Heusler compounds, the LaPtSb exhibits obviously larger power factor at room temperature, especially for the n-type system.Together with the very low lattice thermal conductivity, the thermoelectric figure of merit (ZT) of LaPtSb can be optimized to a record high value of 2.2 by fine tuning the carrier concentration.

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“…This property of the Fe 2 VAl is different from the other class of Heusler compound ZrNiSn. 39 In the latter compounds the electron pockets centered around the X points are heavier than the hole pockets centered around the Γ point. Consequently the magnitude of the thermopower is larger for the electrons in ZrNiSn.…”

Section: Gga Calculationmentioning

confidence: 99%

Effect of onsite Coulomb repulsion on thermoelectric properties of full-Heusler compounds with pseudogaps

Lee

Mahanti

2011

Phys. Rev. B

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Electronic structure calculations using local density and generalized gradient(LDA/GGA) approximations for the full Heusler compound Fe2VAl show that it is a pseudo-gap (negative gap) system with very small density of states (DOS) at the Fermi level but rapidly rising DOS away from it, a feature that makes this compound a promising thermoelectric material. Thermopower (S) measurements in nominally pure and n-doped Fe2VAl give indeed large values of S (∼-150 µV/K at 200 K). To improve on the inadequacy of LDA/GGA in handling d-electron systems and to understand the origin of large thermopowers measured, we have carried out electronic structure calculations using GGA+U method with several values of the on-site Coulomb interaction parameter U including the ones calculated using constrained density functional theory (DFT). For the latter, we found Fe2VAl to be a narrow band gap semiconductor with a gap of 0.55 eV. With the calculated band structures, we have studied the carrier concentration and temperature dependence of S using Boltzmann transport equation in constant relaxation time approximation for both the pseudo-gap and gapped cases.Comparison between theory and experiment suggests that neither the pseudo-gap nor the finite gap (0.55 eV) model can explain all the transport properties consistently. Therefore treatment of U beyond simple mean-field approach (done in GGA+U) and/or inclusion of defect induced changes in the host electronic structure might be important in understanding the experiments.

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Electronic structure of rare-earth nickel pnictides: Narrow-gap thermoelectric materials

Cited by 139 publications

References 22 publications

Validity of the rigid band approximation in the study of the thermopower of narrow band gap semiconductors

Validity of the rigid band approximation in the study of the thermopower of narrow band gap semiconductors

LaPtSb: a half-Heusler compound with high thermoelectric performance

Effect of onsite Coulomb repulsion on thermoelectric properties of full-Heusler compounds with pseudogaps

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