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 st...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 inverted-parabolic behavior—including cases of multiple bands.In contrast to common descriptors(e.g.,quality factor and complexity factor),the degree to which multiple pockets improve thermoelectric performance is bounded by interband scattering and the relative shapes of the bands.We establish that extremely anisotropic“flat-and-dispersive”bands,although best-performing in theory,may not represent a promising design strategy in practice.Critically,we determine optimum bandwidth,dependent on temperature and lattice thermal conductivity,from perfect transport cutoffs that can in theory significantly boost zT beyond the values attainable through intrinsic band structures alone.Our analysis should be widely useful as the thermoelectric research community eyes zT>3.展开更多
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 const...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,coefficient of thermal expansion,and vibrational free energy and entropy.It performs phonon renormalization for dynamically unstable compounds to obtain real effective phonon spectra at finite temperatures and calculates the associated free energy corrections.The methods and parameters are chosen to balance computational efficiency and result accuracy,assessed through convergence testing and comparisons with experimental measurements.Deployment of this workflow at a large scale would facilitate materials discovery efforts toward functionalities including thermoelectrics,contact materials,ferroelectrics,aerospace components,as well as general phase diagram construction.展开更多
基金This work was led by funding from U.S.Department of Energy,Office of Basic Energy Sciences,Early Career Research Program,which supported J.P.and A.J.Lawrence Berkeley National Laboratory is funded by the Department of Energy under award DE-AC02-05CH11231V.O.acknowledges financial support from the National Science Foundation Grant DMR-1611507.This work used resources of the National Energy Research Scientific Computing Center,a Depatment of Energy Office of Science User Facility supported by the Office of Science of the U.S.Department of Energy under Contract No.DE-AC02-05CH11231J.P.thanks Younghak Kwon of UCLA Mathematics for helpful discussions.
文摘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 inverted-parabolic behavior—including cases of multiple bands.In contrast to common descriptors(e.g.,quality factor and complexity factor),the degree to which multiple pockets improve thermoelectric performance is bounded by interband scattering and the relative shapes of the bands.We establish that extremely anisotropic“flat-and-dispersive”bands,although best-performing in theory,may not represent a promising design strategy in practice.Critically,we determine optimum bandwidth,dependent on temperature and lattice thermal conductivity,from perfect transport cutoffs that can in theory significantly boost zT beyond the values attainable through intrinsic band structures alone.Our analysis should be widely useful as the thermoelectric research community eyes zT>3.
基金supported by the Materials Project,funded by the U.S.Department of Energy under award DE-AC02-05CH11231(Materials Project program KC23MP)J.P.acknowledges the support from the U.S.Department of Energy,Office of Basic Energy Sciences,Early Career Research Program+1 种基金J.W.L.and J.P.also acknowledge funding by the Transformational Tools and Technologies(TTT)project of the Aeronautics Research Mission Directorate(ARMD)at the National Aeronautics and SpaceAdministration(NASA).A.M.G.was supported by EPSRC Fellowship EP/T033231/1This work used computational resources of the National Energy Research Scientific Computing Center(NERSC),a Department of Energy Office of Science User Facility supported by the Office of Science of the U.S.Department of Energy under Contract No.DE-AC02-05CH11231.
文摘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,coefficient of thermal expansion,and vibrational free energy and entropy.It performs phonon renormalization for dynamically unstable compounds to obtain real effective phonon spectra at finite temperatures and calculates the associated free energy corrections.The methods and parameters are chosen to balance computational efficiency and result accuracy,assessed through convergence testing and comparisons with experimental measurements.Deployment of this workflow at a large scale would facilitate materials discovery efforts toward functionalities including thermoelectrics,contact materials,ferroelectrics,aerospace components,as well as general phase diagram construction.
