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33
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Introduction
I do first-principles theoretical and computational research in materials science. My general interests include electron and phonon transport, lattice dynamics, phase transitions, and more. Among the class of materials I study are thermoelectrics, battery materials, electronic materials, and shape-memory alloys, either independently or in collaboration with experimentalists.
Current institution
Additional affiliations
February 2019 - June 2021
August 2017 - July 2018
September 2014 - January 2019
Education
September 2014 - March 2019
August 2008 - May 2014
Publications
Publications (33)
Band convergence is considered a clear benefit to thermoelectric performance because it increases the charge carrier concentration for a given Fermi level, which typically enhances charge conductivity while preserving the Seebeck coefficient. However, this advantage hinges on the assumption that interband scattering of carriers is weak or insignifi...
This is a review of theoretical and methodological development over the past decade pertaining to computational characterization of thermoelectric materials from first principles. Primary focus is on electronic and thermal transport in solids. Particular attention is given to the relationships between the various methods in terms of the theoretical...
The observation is made that a linear dispersion in any dimension under acoustic-phonon- deformation-potential scattering theoretically prescribes a constant charge transport distribution, required for the boxcar profile known to maximize the thermoelectric figure of merit. A linear dispersion squeezed by two transport gaps for optimized bandwidth...
Electronic mobility and conductivity of S1−xSex are computed from first-principles throughout the compositional spectrum. This system spans both the band transport domain and the hopping domain due to the inherently semicrystalline, pseudomolecular atomic structure in the form of the packed eight-atom rings. By and large, mobility decreases initial...
Lithium lanthanum zirconium oxide (LLZO) is widely known as the most stable solid electrolyte against lithium metal electrodes. This thermodynamic stability can be lost by the presence of dopants which are required to stabilize the cubic phase of LLZO and can be reduced by lithium metal. However, the role of oxygen in such reactions is taken for gr...
We develop an automated high-throughput workflow for calculating lattice dynamical properties from first principles including those dictated by anharmonicity. The pipeline automatically computes interatomic force constants (IFCs) up to 4th order from perturbed training supercells, and uses the IFCs to calculate lattice thermal conductivity, coeffic...
We develop an automated high-throughput workflow for calculating lattice dynamical properties from first principles including those dictated by anharmonicity. The pipeline automatically calculates interatomic force constants (IFC) up to 4th order from perturbed training supercells, and uses the IFC to calculate lattice thermal conductivity, coeffic...
We develop an automated high-throughput workflow for calculating lattice dynamical properties from first principles including those dictated by anharmonicity. The pipeline automatically calculates interatomic force constants (IFC) up to 4th order from perturbed training supercells, and uses the IFC to calculate lattice thermal conductivity, coeffic...
The temperature dependence of experimental charge carrier mobility is commonly used as a predictor of the dominant carrier scattering mechanism in semiconductors, particularly in thermoelectric applications. In this work, we critically evaluate whether this practice is well founded. A review of 47 state-of-the-art mobility calculations reveals no c...
Observation is made that a linear dispersion in any dimension under acoustic-phonon-deformation-potential scattering theoretically prescribes a constant charge transport distribution, required for the boxcar profile that is known to optimize the thermoelectric figure of merit. A linear dispersion squeezed by two transport gaps under scattering by p...
The density of states of electrons is a simple, yet highly-informative, summary of the electronic structure of a material. Here, some remarkable features of the electronic structure that are perceptible from the density of states are concisely reviewed, notably the analytical E vs. k dispersion relation near the band edges, effective mass, Van Hove...
The electronic transport behaviour of materials determines their suitability for technological applications. We develop a computationally efficient method for calculating carrier scattering rates of solid-state semiconductors and insulators from first principles inputs. The present method extends existing polar and non-polar electron-phonon couplin...
Understanding how to optimize electronic band structures for thermoelectrics is a topic of long-standing interest in the community. Prior models have been limited to simplified bands and/or scattering models. In this study, we apply more rigorous scattering treatments to more realistic model band structures—upward-parabolic bands that inflect to an...
n-type Mg3Sb2-based materials have become a top candidate for efficient thermoelectric applications within 300-700K, due to its high band degeneracy, inherently high carrier mobility and low lattice thermal conductivity, as well as its advantages of less toxicity and abundance. Existing works showed that Mg3Bi2-alloying largely help ensure the exce...
Accurate density functional theory calculations of the interrelated properties of thermoelectric materials entail high computational cost, especially as crystal structures increase in complexity and size. New methods involving ab initio scattering and transport (AMSET) and compressive sensing lattice dynamics are used to compute the transport prope...
Band convergence is considered a clear benefit to thermoelectric performance because it increases the charge carrier concentration for a given Fermi level, enhancing electrical conductivity while preserving the Seebeck coefficient. However, this advantage hinges on the assumption that there is no significant additional interband scattering of carri...
Understanding how to optimize electronic band structures for thermoelectrics is a topic of long-standing interest in the community. Prior models have been limited to simplified bands and/or scattering models. In this study, we apply more rigorous scattering treatments to more realistic model band structures - upward-parabolic bands that inflect to...
We report a first-principles density-functional study of electron-phonon interactions in and thermoelectric transport properties of the full Heusler compounds Sr2BiAu and Sr2SbAu. Our results show that ultrahigh intrinsic bulk thermoelectric performance across a wide range of temperatures is physically possible and point to the presence of multiply...
The electronic transport behaviour of materials determines their suitability for technological applications. We develop an efficient method for calculating carrier scattering rates of solid-state semiconductors and insulators from first principles inputs. The present method extends existing polar and non-polar electron-phonon coupling, ionized impu...
We report first-principles density-functional study of electron-phonon interactions and thermo- electric transport properties of full-Heusler compounds Sr2BiAu and Sr2SbAu. Our results show that ultrahigh intrinsic bulk thermoelectric performance across a wide range of temperatures is physically possible and point to the presence of multiply degene...
The Zintl compound Eu2ZnSb2 was recently shown to have a promising thermoelectric figure of merit, zT~1, due to its low lattice thermal conductivity and high electronic mobility. In the current study, we show that further increases to the electronic mobility and simultaneous reductions to the lattice thermal conductivity can be achieved by isovalen...
Electron-phonon interactions (EPIs) are presumably detrimental for thermoelectric performance in semiconductors because they limit carrier mobility. Here we show that enhanced EPIs with strong energy dependence offer an intrinsic pathway to a significant increase in the Seebeck coefficient and the thermoelectric power factor, particularly in the co...
Electron-phonon interaction (EPI) is presumably detrimental for thermoelectric performance in semiconductors because it limits carrier mobility. Here we show that enhanced EPI with strong energy dependence offers an intrinsic pathway to significant increase in the Seebeck coefficient and the thermoelectric power factor, particularly in the context...
Composed of inexpensive and naturally abundant elements, the chalcopyrite mineral CuFeS2 has received attention as a potentially useful thermoelectric. We use first-principles electronic structure and Boltzmann transport theory calculations to investigate thermoelectric properties of n-doped CuFeS2. We find that energy-dependent carrier lifetimes t...
Intermetallic compounds are usually poor thermoelectrics due to the high electronic densities of states at the Fermi level and concomitantly low Seebeck coefficients. However, intermetallic B20-type CoSi has been experimentally shown to attain remarkably large negative values of the Seebeck coefficient. We provide a theoretical explanation for this...
With first-principles calculations based on density-functional theory, we predict the potential for the unprecedentedly high thermoelectric figure of merit zT=5 at 800 K in an n-type Ba2BiAu full-Heusler compound. Such a high efficiency arises from an intrinsically ultralow lattice thermal conductivity coupled with a very high power factor reaching...
Herein we report the wafer-scale synthesis of thin film black arsenic phosphorus (b-AsP) alloys via two-step solid-source molecular beam deposition (MBD) and subsequent hermetic thermal annealing. We characterized our thin films with a variety of compositional and structural metrology techniques. X-ray photoelectron spectroscopy and energy dispersi...
Using first-principles density-functional theory calculations, we predict the potential for unprecedented thermoelectric efficiency zT= 5 at 800 K in n-type Ba2BiAu full-Heusler compound. Such a high efficiency arises from an intrinsically ultralow lattice thermal conductivity coupled with a very high power factor reaching 7 mW m−1K−2 at 500 K. The...
Using first-principles density-functional theory (DFT) calculations, we predict the potential for unprecedented zT = 5 at 800 K in n-type Ba2BiAu full-Heusler compound. Such a high efficiency arises from intrinsically ultralow lattice thermal conductivity coupled with very high power factor reaching 7 mW m^-1 K^-2 at 500 K. The high power factor or...
Titanium dioxide, with its high refractive index, large bandgap, low thermal expansion, high Kerr nonlinearity, negative thermo-optic coefficient, and intrinsic biocompatibility is an exceptional candidate for applications such as photo voltaics and photocatalysis. On page 711, S. K. Ozdemir, L. Yang, and co-workers mass-fabricate whispering-galler...
